The FBI is investigating campaign fundraising activity involving a company that the head of the U.S. Postal Service formerly led, a spokesman for Postmaster General Louis DeJoy said on Thursday. DeJoy, a supporter of Republican former President Donald Trump who was named to the post in May 2020, has faced criticism from Democrats over mail service changes and a plan to slow some deliveries to save money. DeJoy previously served as chief executive at North Carolina-based New Breed Logistics. The Washington Post first reported the investigation. FBI agents have interviewed current and former DeJoy and New Breed Logistics employees and have issued a subpoena to DeJoy, the Post reported. The Post reported last year that some New Breed Logistics employees said they were pressured by DeJoy or his aides to attend fundraisers or make political contributions to Republicans and then were repaid through bonuses. DeJoy in congressional testimony denied making such reimbursements, calling it an "outrageous claim." New Breed was sold to XPO Logistics Inc (XPO.N) in 2014. Mark Corallo, a DeJoy spokesman, said in a statement that DeJoy "learned that the Department of Justice is investigating campaign contributions made by employees who worked for him when he was in the private sector. He has always been scrupulous in his adherence to the campaign contribution laws and has never knowingly violated them." Corallo said DeJoy "intends to work with DOJ toward swiftly resolving it." The FBI did not immediately respond to a request for comment. A USPS representative declined to comment. The chairwoman of the U.S. House of Representatives Oversight Committee, Carolyn Maloney, said if the allegations are true DeJoy "must resign immediately." She called on the postal board "to immediately disclose what information it had about these allegations and whether it has reviewed them." Some Democrats last year accused DeJoy of making service changes with the intention of impeding the delivery of mail-in ballots for November"s presidential election to help Trump, which DeJoy denied.