A 21-year veteran of the Philadelphia Police Department abruptly retired last week amid a federal probe into whether he was providing a woman with heroin, law enforcement sources said Tuesday.

Commissioner Richard Ross confirmed Tuesday that Stanley Davis Jr., who had been assigned to a federal narcotics task force, was likely to face narcotics-related charges from the U.S. Attorney's Office. Because federal authorities were leading the investigation, Ross said he did not know details of the case or specific counts Davis might face.

Spokeswomen for the U.S. Attorney's Office and the FBI declined to comment.

Attempts to reach Davis were unsuccessful Tuesday.

Sources familiar with the case said authorities were investigating whether Davis, while detailed to the narcotics task force, had supplied a woman with heroin. Details such as how he knew the woman or why he gave her drugs were not immediately clear.

Davis was briefly removed from street duty before retiring last week, sources said.