Federal agents raided the office and home of U.S. Special Counsel Scott Bloch on Tuesday while investigating whether the nation’s top protector of whistleblowers destroyed evidence potentially showing he retaliated against his own staff.

Computers and documents were seized during the raid on the special counsel’s downtown office, according to two law enforcement officials who spoke on condition of anonymity because of the ongoing inquiry. At least 20 agents were still on the scene as of mid-afternoon Tuesday.