Sheriff's Department spokesman Joe Blake tells Action News that the agents served a subpoena and executive search warrants at their office at 100 South Broad Street around 9:00 a.m. Thursday.
"As part of an ongoing investigation begun in the previous administrations, the FBI arrived at the sheriff's office at 100 S. Broad this morning with a search warrant and subpoena for certain records and files," the Sheriff's Department said in a statement.
Agents were seen leaving the building with files and other records.
No arrests were made today and the Sheriff's Department is said to be fully cooperating with the ongoing probe.
Sources tell Action News that investigators were focused on unknown real-estate dealings in the Sheriff's Department.
The FBI is not commenting on the case and the Sheriff's Department will soon release a formal statement on today's operation.
The U.S. Attorney's Office in Philadelphia won't confirm or deny any investigation, says spokeswoman Patricia Hartmann.