Politico reported earlier this week that the FBI has "stepped up inquiries" into the private email server Clinton used during her tenure as secretary of State.

Clinton faced a barrage of questions about her email setup during her lauded appearance last month before the House panel investigating the 2012 Benghazi attack.

Republicans have kept a focus on the issue heading into the second Democratic debate on Saturday night, when Clinton will appear with two other candidates.

"What she did is a crime," Trump added. "She broke the law 100 percent."