FBI Director James Comey is set to testify before a US House committee about the decision to not recommend any charges against Hillary Clinton over her use of personal emails while she was secretary of state.
Mr Comey will be questioned by the US House Oversight Committee tomorrow.
Yesterday, the Bureau sharply rebuked the presumptive Democratic US presidential candidate for her "extremely careless" handling of classified information.
Mrs Clinton served as US secretary of state from 2009 to 2013.
The FBI director said the year-long investigation into the server found that at least 110 emails contained classified information at the time they were sent.
But he said the FBI's judgement was that "no reasonable prosecutor" would bring charges against Mrs Clinton.
Mr Comey told a news conference in Washington yesterday that even though "the Department of Justice makes final decisions on matters like this, we are expressing to Justice our view that no charges are appropriate in this case."
However, in a statement today, Oversight Committee Chairman Jason Chaffetz said that Congress and the American people have a right to understand the FBI’s investigation in the matter.
US House Speaker Paul Ryan has said that Mrs Clinton may have been given preferential treatment from the FBI in its investigation.
When asked by reporters if the former secretary of state received preferential treatment, he replied "It looks like it to me".
Meanwhile US Attorney General Loretta Lynch will testify before the House Judiciary Committee on 12 July on a number of issues facing the Justice Department, including the FBI's probe into Mrs Clinton's use of personal emails.
The panel is also expected to question Ms Lynch on the recent attacks in Orlando, Florida and the attacks last December in San Bernardino, California.
