US President Barack Obama has implicitly criticised FBI director James Comey over the new inquiry into Hillary Clinton’s email use.
He said US investigations should not operate on the basis of “innuendo” or “incomplete information”.
The FBI is now investigating new emails that may be linked to its probe into Mrs Clinton’s private email server.
Mr Comey has faced a fierce backlash for announcing the move just 11 days before the presidential election.
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Mr Obama’s remarks are his first public comments since Mr Comey’s announcement on Friday that the FBI had discovered a new batch of emails that may or may not be relevant to an earlier, closed investigation into Democratic presidential candidate Mrs Clinton’s handling of classified information.
“I’ve made a very deliberate effort to make sure that I don’t look like I’m meddling,” Mr Obama said in an interview with website NowThisNew.
But he added: “I do think that there is a norm that when there are investigations we don’t operate on innuendo, we don’t operate on incomplete information, we don’t operate on leaks. We operate based on concrete decisions that are made.
“When this was investigated thoroughly the last time, the conclusion of the FBI, the conclusion of the justice department, the conclusion of repeated congressional investigations was that she had made some mistakes but that there wasn’t anything there that was prosecutable.”
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It emerged in March 2015 that Mrs Clinton had been breaking federal rules by operating a private email server while she was secretary of state from 2009-13.
Her lawyers combed through the server and provided the state department with 30,000 work-related emails, but her campaign deleted another 33,000 messages, saying they were personal in nature.
Mr Comey concluded in July that Mrs Clinton had been “extremely careless” in handling classified information, but there were no grounds for any charges.
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The latest emails were found in a separate investigation into allegations that former congressman Anthony Weiner sent illicit text messages to a 15-year-old girl in North Carolina. Mr Weiner is married to one of Mrs Clinton’s closest aides, Huma Abedin.
The FBI has reportedly obtained a warrant to search the cache of emails belonging to Ms Abedin, which are believed to have been found on her estranged husband’s laptop.
There are reportedly 650,000 emails to search through on the laptop, but it is unclear who sent or received the emails or what they were about.
Mr Comey and Attorney General Loretta Lynch have said they are working quickly to sift through the newly discovered emails.
Democrats have angrily demanded that the embattled Mr Comey rapidly make public what the agency knows about the new email trove.
On Sunday, the Democratic leader in the US Senate Harry Reid accused Mr Comey of violating an act which bars officials from influencing an election by revealing the bureau was investigating emails possibly linked to Mrs Clinton.
US election 2016: Obama decries Clinton email ‘innuendo’