A U.S. official says a federal investigation involving a former U.S. diplomat and expert on Pakistan is related to counterintelligence.

The official, who was not authorized to discuss the confidential investigation by name and spoke on condition of anonymity, confirmed Friday that law enforcement agents searched the home of Robin Raphel last month.

The investigation was first reported by The Washington Post, which quoted a spokesman for Raphel as saying that she was aware of the investigation. It was not immediately clear if Raphel has a lawyer.

A Justice Department spokesman declined to comment on Friday.

The State Department says it's cooperating and that Raphel's security clearance was revoked last month.

Raphel is a former ambassador to Tunisia and most recently a senior adviser on civilian aid to Pakistan.