Republican Congressman Cory Mills of Florida is under active criminal investigation by the Department of Justice, according to a source familiar with the matter who spoke to Fox News. The exact nature of the alleged offence has not been disclosed, but the investigation adds to mounting legal and political pressure on the lawmaker, who sits on the House Armed Services and Intelligence committees.

Mills is already facing a separate inquiry from the House Ethics Committee over allegations including campaign finance violations, sexual misconduct and dating violence. The emergence of a DOJ criminal probe alongside the ethics investigation significantly raises the stakes for Mills, amid a wider pattern in which embattled members of Congress have opted to resign rather than face expulsion votes.