(with whom FAIRCHILD, Circuit Judge, joins), concurring.
The affidavit upon which the search warrant issued was concededly prepared by the United States commissioner although signed by an FBI agent. Rule 41 *925(c) of the Federal Rules of Criminal Procedure provides in part as follows:
“A warrant shall issue only on affidavit sworn to before the judge or commissioner and establishing the grounds for issuing the warrant. If the judge or commissioner is satisfied that grounds for the application exist or that there is probable cause to believe that they exist, he shall issue a warrant identifying the property and naming or describing the person or place to be searched.”
This Rule of course contemplates that the supporting affidavit be prepared by the affiant and not by the commissioner. The commissioner is not meant to play the dual roles of magistrate and investigator. Cf. In re Murchison, 349 U.S. 133, 137, 75 S.Ct. 623, 99 L.Ed. 942. No prejudice to defendant has been shown, so that reversal is unwarranted. Nevertheless, the practice of having the commissioner prepare any such affidavits should be disapproved in order that it will not recur in any Districts of this Circuit.