OPINION OF THE COURT
Brown, J.On this appeal, defendant challenges, inter alia, the denial, after a hearing, of his motion to suppress certain physical evidence (i.e., $3,700 in marked bills) recovered during a search of his person incident to a warrantless — and it is argued, unlawful — arrest.
*304The only witness called at the suppression hearing was Detective Albert Coletto, who at the time of the arrest was assigned to the Long Island Task Force of the Drug Enforcement Administration. He testified that, on January 23, 1980, as part of an undercover buy-and-bust operation, he had followed a suspect, Police Officer Leroy Bennett, from the latter’s apartment in Queens County to a candy store in Kings County. Earlier in the day an undercover officer had supplied Bennett with marked currency. Based upon information obtained through the use of authorized telephone wiretaps, the police knew that Bennett was going to the candy store to transact a cocaine sale on behalf of the undercover officer. Armed with this information, the police obtained a warrant to search the premises for the marked currency, cocaine and materials used in the packaging and distribution of cocaine. Detective Coletto testified that, while his superiors were securing that warrant, he watched Bennett enter the store and that he remained on the scene after Bennett’s departure in order to aid his fellow officers in the execution of the warrant. Upon being informed that the warrant had been issued, the officers, who were in plain clothes, entered the premises with guns drawn, displayed their shields and identified themselves as police officers. Detective Coletto stated that he observed at that time that the store was divided into two parts by a counter topped with a plexiglass shield which ran the width of the store. He also noted that in the rear portion of the store, behind the counter, there was a back room.
When the officers entered, there were four people in the store, including defendant. All were in the nonpublic area behind the counter, and one of them (but not the defendant) was in the back room. At the sight of the officers, the other three fled into the back room. Some of the officers then went behind the counter in an effort to apprehend the fleeing men, while others went around to the outside rear of the store to block any escape. Eventually, the officers were able to gain entrance to the back room where they apprehended the four individuals and brought them to the front of the store. After frisking them for weapons, the four were detained in the front of the store while the officers conducted a search of the premises pursuant to the search *305warrant. As a result of that search, three handguns and a quantity of cocaine were recovered from concealed locations in the back room. At that point all four men were placed under arrest and searched as an incident thereto. In searching defendant the police discovered $3,700 of the marked currency in his breast pocket. The balance of the marked currency, $700, was found in the possession of one of the other men, Marrero, the owner of the store.
The hearing court denied the motion to suppress, concluding, inter alia, that the police officers who had knowledge of the drug transaction which had transpired on the premises viewed the flight of the four individuals more seriously than one might view a person simply leaving a room under ordinary circumstances, particularly when coupled with the fact that they had announced their purpose and authority and had identified themselves by displaying their shields. The hearing court found that these facts, taken together with the contraband discovered in the back room, were sufficient to constitute probable cause to arrest. We affirm.
The validity of the search of defendant’s person is dependent upon whether there was probable cause to arrest him. Looking at all the facts here present, we find that there was probable cause for the warrantless arrest of defendant. In viewing the facts, it must be recognized that the existence of probable cause to arrest requires not “evidence sufficient to warrant a conviction * * * but merely information which would lead a reasonable person who possesses the same expertise as the [arresting] officer to conclude, under the circumstances, that a crime is being or was committed” (People v McRay, 51 NY2d 594, 602; People v Valentine, 17 NY2d 128). In the case at bar, the police knew that the premises were being used for drug trafficking and they knew that Bennett had gone into the store just prior to the raid for purposes of a drug transaction and thus could anticipate that the other participant or participants in the transaction were in the premises. At the time they entered the store defendant was in the nonpublic area of the store — as were the other three individuals — thus diminishing any probability that he was simply an ordinary customer. It is clear that ordinarily an individual’s *306mere presence at the scene of a drug transaction or other criminal activity does not itself constitute probable cause (see Ybarra v Illinois, 444 US 85; People v Costales, 39 NY2d 973; People v Martin, 32 NY2d 123; see, also, People v Nieves, 36 NY2d 396). In Martin, however, while finding a lack of probable cause to arrest the defendant in that case, the court also added a caveat that “under certain circumstances * * * presence at the scene might furnish a trained policeman with probable cause to effect an arrest” (People v Martin, supra, p 125). Such circumstances exist in this case. Upon the entry of the police, defendant fled into a back room and concealed himself for a time. This flight and resultant furtive conduct, which might have afforded defendant an opportunity to dispose of any contraband, could readily have been viewed by the police as conduct indicating that defendant was involved in the drug transaction on the premises. As the Supreme Court stated in Sibron v New York (392 US 40, 66-67), “deliberately furtive actions and flight at the approach of strangers or law officers are strong indicia of mens rea, and when coupled with specific knowledge on the part of the [arresting] officer relating the suspect to the evidence of crime, they are proper factors to be considered in the decision to make an arrest” (see, also, People v Sbraccia, 92 AD2d 628). Thus, in our view, probable cause to arrest defendant existed at the time defendant was apprehended in the back room, based upon defendant’s presence at the known drug trafficking location and his flight and furtive conduct upon the arrival of the police.
The instant case is distinguishable from those in which an individual merely happens to be on the scene or arrives on the scene during the execution of a search warrant for a premises which police suspect is connected with narcotics or other criminal activity (see, e.g., Ybarra v Illinois, 444 US 85, supra; People v Costales, 39 NY2d 973, supra; People v Nieves, 36 NY2d 396, supra). Here, defendant, who was at the scene of a drug transaction, did not play the role of an unaware innocent bystander; rather, he fled and successfully concealed, if only momentarily, himself and his activities from the police.
Moreover, even if probable cause to arrest did not exist at the time defendant was initially detained, it cannot be *307gainsaid that upon discovery of the cocaine and weapons in the back room there existed probable cause to believe that the four individuals who had secreted themselves in that room upon the arrival of the police were involved in criminal activity. Accordingly, the arrest made subsequent to that discovery and the search incident thereto were lawful.
The concept of probable cause, as its very name implies, deals with probabilities. The rules for its application are not technical but rather concern the “factual and practical considerations of everyday life on which reasonable and prudent men * * * act” (Brinegar v United States, 338 US 160, 175). In this case, those considerations and probabilities supported a reasonable conclusion by the police that defendant was involved in drug transactions on the premises. Thus, there was probable cause to make the arrest and the physical evidence was lawfully seized pursuant to that arrest.