WASHINGTON  The office of the official responsible for protecting federal workers from political interference was raided by F.B.I. agents on Tuesday as part of an investigation into whether he himself mixed politics with official business.

The raid took place at the office of Scott J. Bloch, the head of the Office of Special Counsel. Computers and documents were seized by agents trying to determine whether Mr. Bloch obstructed justice by hiring an outside company to “scrub” his computer files, The Associated Press reported. Investigators also searched Mr. Bloch’s home in suburban Virginia after obtaining a subpoena.

“It is not clear to us what they are searching for,” James Mitchell, a spokesman for the office, told Reuters. “We are cooperating with law enforcement.” Mr. Mitchell said about 20 agents from the Federal Bureau of Investigation took part in the raid.

The Office of Special Counsel gives advice to federal employees on which activities are proper and which are not allowed under the Hatch Act, which is supposed to guard against direct political interference in governmental affairs. Mr. Bloch’s duties including shielding whistle-blowers who disclose such political meddling.