Commissioner Charles Ramsey confirmed the investigation at a news conference on another matter Friday, the Philadelphia Inquirer (http://bit.ly/1dEIrys ) reported.
Ramsey's comments marked the first time the city has publicly acknowledged the investigation, which the U.S. Attorney's Office has continued to refuse to confirm or deny. The city's Internal Affairs office and corruption task force have been working with the FBI and federal prosecutors on the grand jury investigation, Ramsey said.
Four narcotics officers, and two others who work closely with them, have been reassigned to desk duty and been made to surrender their weapons, according to a department spokeswoman. The Associated Press is not identifying those officers because they've not been criminally charged.
The seventh officer, Jeffrey Walker, has been in custody since his arrest by federal authorities in May.
A federal magistrate has ordered Walker remain jailed until he can stand trial on charges he used his position as a police officer to take personal property, money and marijuana from others.
Federal court records show Ramsey was recorded bragging about how easy it was to rob drug dealers. His defense attorney, Thomas Fitzpatrick, could not be reached by phone on Saturday and didn't immediately respond to an email seeking comment.
Walker conceded that federal prosecutors had enough probable cause to charge him with a crime, and waived a preliminary hearing on the matter in May, court records show.
City police have dismissed charges in hundreds of drug-related arrests since the other officers were transferred from narcotics duty in December 2012 and has also been sued about 40 times in federal court, in connection with alleged misconduct by the officers in question, the newspaper reported. Some of the lawsuits allege the officers framed people with bogus evidence and testimony.
Public defender Bradley Bridge, whose office represented many of the defendants in those cases, applauded the investigation.
"That these officers have now been taken off the street is significant," Bridge said. "Substantial questions have arisen regarding the propriety of their actions while making arrests. Until those questions have been answered satisfactorily, the most prudent course is to prevent them from making more questionable arrests."