(CNN) An independent federal investigative agency is looking into whether acting Attorney General Matthew Whitaker violated prohibitions on political activities by federal employees by accepting contributions to his 2014 Senate campaign earlier this year.

Last January and February, when Whitaker served as chief of staff at the Department of Justice, four individuals donated a total of $8,800 to the committee for Whitaker's unsuccessful 2014 run for a Senate seat in Iowa, according to Federal Election Commission records.

Austin Evers, the executive director of the watchdog organization American Oversight, told CNN his group submitted a complaint to the Office of Special Counsel that argued Whitaker may have violated the Hatch Act, which prohibits federal employees from accepting political contributions.

A spokesperson for the Office of Special Counsel confirmed receipt of the complaint and said a case file on the matter has been opened. The office can investigate Hatch Act complaints and recommend discipline but does not directly take disciplinary action. The office has no connection to the Justice Department special counsel's office that is overseeing Russian interference in the 2016 US election.