The defendant was convicted in the Superior Court of possession of marihuana and LSD, and possession with intent to sell the same. He appealed under G. L. c. 278, §§ 33A-33G, and the Appeals Court reversed the judgments below. Commonwealth v. Forde, 2 Mass. App. Ct. 425 (1974). The Commonwealth applied for and was granted further appellate review pursuant to G. L. c. 211 A, § 11. The opinion of the Appeals Court contains a full statement of the facts and we repeat here only those critical to our decision.
The warrantless entry into the defendant’s apartment, which had been under police surveillance for some six months prior thereto, occurred about 11:45 p.m. on January 27, 1971. Earlier that month Sergeant Henry J. Rinaldi (Rinaldi) of the Boston police had been in receipt of information from a reliable informant relative to drug sales made by persons resident in the apartment. Approximately a week before January 27, 1971, the informant described having been in the apartment a few days earlier where he witnessed a sale of marihuana to a third person. Rinaldi testified that he had planned to obtain a search warrant in the week that followed but had not done so. At 7 p.m. on January 27, Rinaldi learned that one Donald McDonald would be arriving at the apartment that evening to purchase marihuana. Rinaldi and another officer “staked out” the building and observed McDonald entering the apartment and leaving with a shopping bag. They followed McDonald’s car for several blocks and arrested McDonald and the three other occupants of the car. Marihuana was found in the shopping bag. The four persons arrested were taken to police headquarters.
Based on the testimony of the police, the only activities which occurred between 8:30 p.m., the time of the arrest, and 11:30 p.m., were booking, photographing, and fingerprinting three of the four arrested persons, as well as calling the parents of the fourth, a juvenile, so that she might be released to them that evening. At *80011:30 p.m. Rinaldi called an assistant district attorney to inquire whether he could search the defendant’s apartment without a warrant. The answer was in the negative. While he was still on the telephone, another officer came to Rinaldi to inform him that he had just overheard McDonald telling two of his companions who were about to be admitted to bail that “they better get right down to the place and tell them what has happened because, 1 can’t get bailed.’” Rinaldi then attempted to telephone two assistant clerks of the Municipal Court of the Roxbury District in order to procure a warrant. At 11:45 p.m. , having failed to reach either of these clerks, he and seven other police officers proceeded to the defendant’s apartment, rang the doorbell, and immediately arrested all of the occupants, fanning out through the apartment in the process. Those arrested were taken to police headquarters. About 1 a.m. Rinaldi finally reached one of the assistant clerks to obtain a search warrant issued entirely on the evidence in plain view at the time of the initial entry. Shortly after 2 a.m. a thorough search of the apartment was conducted.
In justification of the initial warrantless entry, the Commonwealth first argues that the cases fall within the exception to the warrant requirement in that the officers were faced with exigent circumstances. The Appeals Court rejected this contention, 2 Mass. App. Ct. 425, 429-430 (1974), and we are of the same opinion. When searches are conducted without a warrant, the burden is on the government “to show that a particular search falls within a narrow class of permissible exceptions.” Commonwealth v. Antobenedetto, 366 Mass. 51, 57 (1974). Commonwealth v. Cavanaugh, 366 Mass. 277, 279 (1974). Commonwealth v. Hall, 366 Mass. 790, 801-802 (1975) . Vale v. Louisiana, 399 U. S. 30, 34 (1970). Under the exception for exigent circumstances, there must be a showing that it was impracticable for the police to obtain a warrant, and the standards as to exigency are strict. McDonald v. United States, 335 U. S. 451, *801454-456 (1948). Vale v. Louisiana, supra, at 35. Commonwealth v. Hall, supra.
The exigency here is said to spring from the statement of McDonald to his companions about to be released that the occupants of the defendant’s apartment must be warned. Presumably such a warning would result in the destruction or removal of the drugs. The police had every reason to believe that there were persons in the apartment at that time who could respond to such a warning, so the concern of the police was genuine. Cf. Commonwealth v. Hall, supra, at 802; Vale v. Louisiana, supra, at 34; United States v. Basurto, 497 F. 2d 781, 789 (9th Gir. 1974). Considered alone, the conversation which was overheard could be said to supply exigent circumstances obviating the necessity of a warrant in that the delay in obtaining it would substantially increase the risk of loss or destruction of evidence. Commonwealth v. Hall, supra, at 803-804. United States v. Rubin, 474 F. 2d 262, 269 (3d Cir. 1973), cert. den. sub nom. Agran v. United States, 414 U. S. 833 (1973). United States v. Evans, 481 F. 2d 990, 992 (9th Cir. 1973).
However, the claim of exigency cannot be evaluated without considering the circumstances in their totality. Here the police had been watching the apartment with an eye to drug traffic for some time, and as of at least a week before the raid the police had information sufficient to establish probable cause. See Commonwealth v. Stevens, 362 Mass. 24, 26-28 (1972). The police had planned to get a search warrant during that week but had not done so. On the night of January 27, 1971, after McDonald and his companions were arrested, three hours had elapsed before the police overheard McDonald urging that the occupants of the apartment be warned. During those hours the police undoubtedly could have foreseen the serious risk that one of those arrested would be released that evening and would attempt to warn the defendant and others. See United States v. Mapp, 476 *802F. 2d 67, 74 (2d Cir. 1973); United States v. Evans, supra, at 994. Rinaldi in fact testified that he had called the parents of the arrested female juvenile and announced his intention to release her to them that evening. In these circumstances the failure of the Commonwealth to offer any explanation why no effort was made to obtain a warrant in the three hours prior to the McDonald conversation which was overheard is fatal to its claim of exigency. “Haste does not become necessary in the present sense if the need for it has been brought about by deliberate and unreasonable delay. This would allow the exception to swallow the principle.” Niro v. United States, 388 F. 2d 535, 540 (1st Cir. 1968). United States v. Curran, 498 F. 2d 30, 34 (9th Cir. 1974). United States v. Rosselli, 506 F. 2d 627, 630-631 (7th Cir. 1974). See United States v. Rubin, 474 F. 2d 262, 270 (3d Cir. 1973), cert. den. sub nom. Agran v. United States, 414 U. S. 833 (1973). Cf. Commonwealth v. Duran, 363 Mass. 229, 231-232 (1973). We do not intimate that the emergency which developed at 11:30 p.m. was contrived by the police but since as an emergency it was easily foreseeable, and since the police had three hours in which they might have secured a warrant and thereby avoided the need to rely on the emergency justification, see United States v. Rosselli, supra, the police must offer some acceptable explanation for their failure to act in that time. We hasten to add that our decision does not imply that police must be required to conduct a search as soon as probable cause arises. See Cardwell v. Lewis, 417 U. S. 583, 595-596 (1974). Nor must a warrant be obtained at that stage of the investigation, for the warrant would then have to be executed within seven days at most. G. L. c. 276, § 2A. Commonwealth v. Cromer, 365 Mass. 519, 525-526 (1974). Furthermore, where the police are conducting an investigation of continuing criminal activities, the exigency of circumstances which develop unexpectedly is not diminished by the fact that in hindsight it appears that there would *803have been time to obtain a warrant. United States v. Titus, 445 F. 2d 577, 578-579 (2d Cir. 1971), cert. den. 404 U. S. 957 (1971). United States v. Miller, 460 F. 2d 582, 586 (10th Cir. 1972). United States v. Davis, 461 F. 2d 1026, 1031 (3d Cir. 1972). We hold here only that where the exigency is reasonably foreseeable and the police offer no justifiable excuse for their prior delay in obtaining a warrant, the exigency exception to the warrant requirement is not open to them.
The Commonwealth argues alternatively that the entry into the defendant’s apartment was for the purpose of making arrests and that no “search” in the terms of the Fourth Amendment to the United States Constitution occurred until after a warrant was finally obtained, for the only items “seized” initially were those in plain view. The Appeals Court concluded that there was probable cause to make the arrests, and that under the Commonwealth precedents a warrant was not required for an arrest even though it entailed an entry into a dwelling and even though the police may have had time to obtain a warrant. However, the Appeals Court also concluded that while the arrests were valid, a search incident to the arrest could not be justified where there were no exigent circumstances excusing the lack of a search warrant. 2 Mass. App. Ct. 425, 432 (1974).
As to the latter conclusion, we are not in agreement. The only evidence “seized” prior to obtaining the search warrant was that which was in plain view to the police in the course of making the arrests. Its discovery did not constitute a “search” within the meaning of the Fourth Amendment. Commonwealth v. Haefeli, 361 Mass. 271, 280 (1972). Ker v. California, 374 U. S. 23, 43 (1963). The requirement of “inadvertent” discovery imposed by Coolidge v. New Hampshire, 403 U. S. 443, 469-471 (1971), which was designed to prevent general warrantless searches when the police know what they are looking for and have time to seek a warrant, does not apply to items in plain view within the scope of a limited search *804incident to arrest as permitted by Chimel v. California, 395 U. S. 752 (1969). See Coolidge v. New Hampshire, supra, at 465, n. 24, 482. It does not appear that the limits of Chimel were transgressed. Therefore, if the arrests were valid the items in plain view could be seized, and observations made by the police while making the arrests could provide the basis for the subsequent issuance of a search warrant.
We are thus led to turn to the validity of the arrests. The traditional common law rule in Massachusetts as to entry of a dwelling to make an arrest was that stated by the court in Commonwealth v. Phelps, 209 Mass. 396, 407-408 (1911): “An officer who has the right to arrest without a warrant because he suspects on reasonable grounds that the defendant has committed a felony, has a right to break open doors.” More recently, in Commonwealth v. Andrews, 358 Mass. 721, 723-725 (1971), we upheld the validity of a warrantless entry into the defendant’s apartment to arrest the defendant who had been brandishing a gun and threatening to kill everyone in the building. But the issue whether a warrantless entry into a dwelling must be justified by exigent circumstances was not present in that case, for it presented a classic example of the type of emergency which always excuses the failure to obtain a warrant. See Warden, Md. Penitentiary v. Hayden, 387 U. S. 294, 298-299 (1967).
Soon after this court’s decision in the Andrews case, the United States Supreme Court discussed the issue of warrantless entries to make arrests in Coolidge v. New Hampshire, 403 U. S. 443 (1971). The court found it unnecessary to decide the question,1 but in dicta the plurality opinion stated: “It is clear, then, that the notion that the warrantless entry of a man’s house in order to arrest him on probable cause is per se *805legitimate is in fundamental conflict with the basic principle of Fourth Amendment, law that searches and seizures inside a man’s house without warrant are per se unreasonable in the absence of some one of a number of well defined ‘exigent circumstances.’” Id. at 477-478. The right of police officers to enter into a home, for whatever purpose, represents a serious governmental intrusion into one’s privacy. It was just this sort of intrusion that the Fourth Amendment was designed to circumscribe by the general requirement of a judicial determination of probable cause. Agnello v. United States, 269 U. S. 20, 32-33 (1925). Johnson v. United States, 333 U. S. 10, 14 (1948). Wolf v. Colorado, 338 U. S. 25, 27-28 (1949). United States v. United States Dist. Court for the E. Dist. of Mich. 407 U. S. 297, 313 (1972). Dorman v. United States, 435 F. 2d 385, 389-390 (D. C. Cir. 1970). LaFave, Warrantless Searches and the Supreme Court: Further Ventures into the “Quagmire,” 8 Crim. Law Bull. 9, 28 (1972). Note, 23 Stanford L. Rev. 995, 997-999 (1971). The distinction between an entry to search and an entry to arrest is slight, for the latter may well be characterized as simply a search for a person rather than a search for things. See Warden, Md. Penitentiary v. Hayden, supra;2 Morrison v. United States, 262 F. 2d 449, 452 (D. C. Cir. 1958). Moreover, it can be argued that an entry to arrest is a far greater intrusion than an entry to search. Coolidge v. New Hampshire, supra, at 479-480. The exigencies which would excuse the lack of an arrest warrant may *806differ from those supplying the excuse for the lack of a search warrant. In any event, the police are required to demonstrate that exigency. In short, we believe that the Fourth Amendment prohibits a warrantless entry into a dwelling to arrest in the absence of sufficient justification for the failure to obtain a warrant.3 While this conclusion departs from the old law of the Commonwealth, the same result has been reached by nearly every court to address the issue in recent years. Dorman v. United States, 435 F. 2d 385, 388-391 (D. C. Cir. 1970). Vance v. North Carolina, 432 F. 2d 984, 990-991 (4th Cir. 1970). United States v. Shye, 492 F. 2d 886, 891 (6th Cir. 1974). United States v. Phillips, 497 F. 2d 1131, 1135 (9th Cir. 1974). Salvador v. United States, 505 F. 2d 1348, 1351-1352 (8th Cir. 1974). United States v. Weinberg, 345 F. Supp. 824, 837-838 (E. D. Pa. 1972), affd. in part 478 F. 2d 1351 (1973), cert. den. 414 U. S. 1005 (1973). United States v. Rodriguez, 375 F. Supp. 589, 593 (S. D. Tex. 1974), affd. 497 F. 2d 172 (5th Cir. 1974). Huotari v. Vanderport, 380 F. Supp. 645, 649-651 (D. Minn. 1974). People v. Moreno, 176 Colo. 488, 497 (1971). See Wheeler v. Goodman, 330 F. Supp. 1356, 1371 (W. D. N. C. 1971) (holding not limited to arrests in dwellings); Stuck v. State, 255 Ind. 350, 356-358 (1970) (arrest warrant must be secured whenever practicable); Nilson v. State, 272 Md. 179, 185-191 (1974) (assuming exigent circumstances are a constitutional prerequisite to warrantless entry to arrest, such circumstances were present). Contra, United States ex rel. Falconer v. Pate, 319 F. Supp. 206, 212 (N. D. Ill. 1970), affd. without opinion, 478 F. 2d 1405 (7th *807Cir. 1973), cert. den. 414 U. S. 1094 (1973); State v. Perez, 277 So. 2d 778, 782-783 (Fla. 1973), cert. den. 414 U. S. 1064 (1973).
It is our view that there were no exigent circumstances here excusing the lack of an arrest warrant. Factors which would have tended to support a finding of exigency include a showing that the crime was one of violence or that the suspect was armed, a clear demonstration of probable cause, strong reason to believe that the suspect was in the dwelling, and a likelihood that the suspect would escape if not apprehended. Additional considerations testing the reasonableness of police conduct are whether the entry is peaceable and whether the entry is in the nighttime. Dorman v. United States, 435 F. 2d 385, 392-393 (D. C. Cir. 1970). The police action with which we are here concerned finds little support in these factors. It is impossible to find one’s way around the delay of three hours in seeking the warrants. In the face of this delay the possible warning of the defendant which most likely would have been directed-toward the destruction of evidence rather than his escape does not achieve the level of an exigency.
Since the warrantless arrests in the defendant’s apartment were invalid, the police had no legal justification for being present in the apartment and cannot rely on the “plain view” doctrine for a warrantless seizure of contraband. Coolidge v. New Hampshire, 403 U. S. 443, 466 (1971). Commonwealth v. Haefeli, 361 Mass. 271, 281-282 (1972). As to the search warrant obtained after the entry into the apartment, it is apparent that the affidavit in support of the warrant is based solely on information acquired during that initial illegal entry. Consequently, evidence seized pursuant to the warrant should have been suppressed. Wong Sun v. United States, 371 U. S. 471, 484-488 (1963). Commonwealth v. Penta, 361 Mass. 894, 895 (1972). Common*808wealth v. Hall, 361 Mass. 790, 795 (1975). It follows that the judgments of the Superior Court must be reversed.
So ordered.
The question remains unanswered by the Supreme Court. See Johnson v. Louisiana, 406 U. S. 356, 365 (1972); Gerstein v. Pugh, 420 U. S. 103, 113, n. 13 (1975).
The Hayden case not only treated an entry to arrest as a search of the dwelling for a person but also excused the lack of a warrant on the ground that exigent circumstances were present. As the plurality opinion in Coolidge v. New Hampshire, supra, at 480-481, stated: “The case of Warden v. Hayden . . ., where the Court elaborated a ‘hot pursuit’ justification for the police entry into the defendant’s house without a warrant for his arrest, certainly stands by negative implication for the proposition that an arrest warrant is required in the absence of exigent circumstances.”
Our holding does not imply that warrantless arrests in general must be justified by exigent circumstances excusing the lack of a warrant but, rather, is limited to warrantless entries of dwellings for the purpose of making arrests within those dwellings. See Gerstein v. Pugh, 420 U. S. 103, 113, n. 13 (1975). Cf. United States v. Watson, 504 F. 2d 849 (9th Cir. 1974), cert. granted 420 U. S. 924 (1975) (invalidating warrantless arrest in a public place).