The inspector general's announcement comes amid outcry from Democrats who say Clinton's loss to President-elect Donald Trump was in part due to Comey's bringing Clinton's emails back into the public spotlight less than two weeks before the 2016 election.

The Justice Department's Office of Inspector General said the probe would focus in part on decisions leading up to public communications by FBI Director James Comey regarding the Clinton investigation, and whether underlying investigative decisions may have been based on "improper considerations." Although the FBI ultimately decided not to refer Clinton's case for prosecution, Comey aroused suspicion that may have diminished trust in Clinton among voters.

The FBI's role in Clinton's unexpected defeat in November has remained a subject of fierce debate — with Comey himself in the middle of the controversy. Clinton's campaign has blamed Comey and the FBI for her loss to President-elect Donald Trump. Eleven days before Election Day, Comey sent a letter to lawmakers telling them investigators had uncovered emails that appeared to be pertinent to the bureau's probe, considered completed at the time, of Clinton's private email server and her handling of classified material while secretary of State.

The announcement exploded in the final days of the campaign. And with a subsequent letter from Comey, a Republican nominated by Obama to his position, saying the emails had turned up no new evidence did little to quell the storm.