FBI director defends decision in Hillary Clinton email case
FBI Director James Comey defended his recommendation not to charge Hillary Clinton over her use of private email during a Congressional hearing.
Republicans said Mrs Clinton received special treatment and compromised national security.
However, Mr Comey testified that she did not break the law or mislead investigators.
Mrs Clinton, the presumptive Democratic presidential nominee, used private email servers while secretary of state.
She said she used the email servers for convenience and said she did not send or receive classified information.
House Speaker Paul Ryan said Mr Comey's recommendation proves Mrs Clinton is "living above the law" and questioned whether she should be briefed on classified information as a presidential candidate.
Mr Comey said he and the FBI investigated the case in a "professional and apolitical way".
Analysis: Anthony Zurcher, BBC News North America Reporter
"No reasonable prosecutor would bring this case," FBI Director James Comey said of his recommendation that Hillary Clinton not charged for her use of a private email server. "I know that frustrates people."
It certainly had Republicans up in arms, expressing incredulity at Comey's assertions that Mrs Clinton set up her server for "convenience" and that she did not instruct her lawyers to permanently delete all her emails they deemed personal.
Perhaps the biggest news, however, came when committee chairman Jason Chaffetz said he would instruct the FBI to investigate whether Mrs Clinton lied when she told Congress under oath that she did not email classified information. Mr Comey said that this was a matter previously outside his purvey.
On Tuesday we learned the number of Clinton emails bearing classified markings - three - and that the markings were the letter "c" in parenthesis in front of paragraphs that contained classified details.
Mr Comey said, however, that Mrs Clinton may not have known this denoted the presence of classified information.
It was another chance for Republicans to express shock and outrage. And given that the FBI could be back in the Clinton-investigating business, it likely won't be the last.
The FBI found more than 100 pieces of classified information on the servers.
Mr Comey said Clinton and her staff were "reckless" but no "reasonable prosecutor" would bring forth criminal charges in the case.
"If your name isn't Clinton, or you're not part of the powerful elite, then Lady Justice will act differently,'' Republican Representative from Utah Jason Chaffetz said.
He said the FBI set a "dangerous precedent" in recommending not charging Mrs Clinton.
Mr Comey said the "c" markings were in the body of the emails and not at the top where they would have been more visible.
Democratic members of the committee holding the hearing said Republicans were using it as way to hurt Mrs Clinton politically.
"This should be called out for what it is, another blatant political stunt by Republicans to try and keep the issue alive after career DOJ officials declared the case closed because they didn't get the outcome they wanted," a Clinton campaign official said in a statement.