Several FBI agents raided the Peoria campaign office of former Congressman Aaron Schock on Thursday.
A nearby business owner says the agents spent more than six hours at the office loading multiple boxes into a truck.
The move comes a day after Schock's executive assistant testified before a federal grand jury investigating allegations of the Republican’s improper spending.
The U.S. Attorney's office spokeswoman Sharon Paul declined to comment.
Prosecutors began reviewing Schock's travel expenses and spending after reports surfaced that he elaborately decorated his Capitol Hill office. He spent about $50,000 for the makeover inspired by the television show "Downton Abbey."
Schock resigned in March amid the spending allegations.