A U.S. federal agency has opened a formal investigation into former special counsel Jack Smith, who oversaw two criminal probes into President Donald Trump following his first term in the White House.

The Office of Special Counsel confirmed that it was investigating whether Smith violated the Hatch Act, a law prohibiting federal employees from using their position for political activity. The decision follows a request for a probe by U.S. Sen. Tom Cotton, an Arkansas Republican.

The OSC is an independent agency that probes the conduct of federal employees, but it does not have the authority to bring criminal charges. It is different from the type of Special Counsel's office previously overseen by Smith, who was appointed by the Department of Justice to pursue criminal cases.