A watchdog is to investigate the actions of the US Department of Justice and the FBI in the months leading up to last year's election, amid the controversy over Hillary Clinton's private email server.
The department's inspector-general Michael Horowitz said his investigation will look at whether correct policies were followed by FBI director James Comey.
Democrats have blamed Mr Comey's handling of the emails investigation, and his late-October release of a letter about the case, as a reason for Mrs Clinton's loss to Republican Donald Trump.
Mr Horowitz said the investigation will look at whether department or FBI policies were followed in relation to Mr Comey's actions in the case, whether the FBI deputy-director should have been recused from the investigation, and allegations that department officials improperly disclosed non-public information to the Clinton campaign.
The review will examine Mr Comey's news conference in July in which he said the FBI would not recommend charges.
During his announcement, Mr Comey delivered an unusual public statement for an FBI chief by chastising Mrs Clinton and her aides as "extremely careless".
It will also review the two letters he sent to Congress about the case in the final days before the election.
Mrs Clinton and her aides said the disclosure of "new" emails - found on a laptop belonging to Anthony Weiner, the estranged husband of the Democrat candidate's aide Huma Abedin - less than two weeks before election day damaged her in several battleground states.
Mr Comey's action prompted outrage from Mrs Clinton and other Democrats, who said it needlessly placed her under suspicion when the FBI did not even know if the emails were relevant.