An estimated 200 FBI and IRS agents served search warrants at county offices and homes in Cleveland.
FBI spokesman Scott Wilson says he can't comment on anything that's being searched or seized. But he says Monday's activity stems from a long-term public corruption probe.
Hundreds of FBI agents descended on the Cuyahoga County Administration building in Cleveland, and agents also searched the county engineer's office.
Staffers at the county's information services center say they were told they could go home because they wouldn't be able to work.