WASHINGTON (REUTERS) - FBI director James Comey came under pressure on Sunday (Oct 30) to quickly disclose details of the newly discovered e-mails related to Mrs Hillary Clinton's private server, but the bureau must obtain a search warrant before agents can even examine the e-mails.
Sources familiar with the matter said the FBI had concluded it could not thoroughly explore the material without additional legal authorisation in the form of a search warrant, which would normally require approval from a judge or magistrate.
The process could scuttle any hopes of a swift resolution to the probe, raising the possibility of a prolonged controversy that could extend beyond the Nov 8 election and cast a shadow over a Clinton transition if she wins the White House.
Mr Comey's disclosure of the new e-mails on Friday (Oct 28) plunged the final days of the White House race between Democrat Clinton and Republican Donald Trump into turmoil. Mrs Clinton had opened a recent lead over Mr Trump in national polls, but it had been narrowing even before the e-mail controversy resurfaced.
Top Clinton aides lashed out at Mr Comey on Sunday for revealing the bureau's probe of the newly found e-mails and renewed their demands that he quickly release details about the discovery.
Clinton campaign chairman John Podesta and campaign manager Robby Mook questioned Mr Comey's decision to send a letter notifying Congress of the e-mail review before he even knew whether they were significant or relevant.
Mr Comey's letter was "long on innuendo, short on facts", Mr Podesta said on CNN's State of the Union programme, and accused the Federal Bureau of Investigation chief of breaking precedent by disclosing aspects of an investigation so close to the election.
"We are calling on Mr Comey to come forward and explain what's at issue here," Mr Podesta said, adding the significance of the e-mails was unclear.
"He might have taken the first step of actually having looked at them before he did this in the middle of a presidential campaign, so close to the voting," Mr Podesta said.
Mr Comey's letter was sent over the objections of Justice Department officials. Under standard procedures, the FBI would ask a federal prosecutor working for the Justice Department to seek such a warrant.
But that scenario may be complicated because the Justice Department has signalled its dismay with Mr Comey's decision to publicly disclose the bureau's interest in the newly discovered e-mails.
FBI officials were unavailable for comment on the status of their investigation.
Mr Trump has highlighted the issue as proof for his argument that Mrs Clinton is corrupt and untrustworthy.
'THE WAY TO BEAT CORRUPTION'
"We have one ultimate check on Hillary's corruption and that is the power of the vote," Mr Trump told a rally in Las Vegas on Sunday. "The only way to beat the corruption is to show up and vote by the tens of millions."
Mr Comey, who announced in July that the FBI's long investigation of Mrs Clinton's e-mails during her time as secretary of state was ending without any charges, said in his letter the agency would review the newly surfaced e-mails to determine their relevance to the investigation of her handling of classified information.
Clinton campaign manager Mook said on Fox News Sunday: "If there is new information, get it out on the table."
He added that the e-mails could be duplicates of previously reviewed e-mails. "Again, it's been reported these e-mails may not have been sent or received by Secretary Clinton. We don't know anything."
An ABC News/Washington Post poll released on Sunday showed Mrs Clinton with a statistically insignificant one-point national lead on Mr Trump. About a third of likely voters in the poll said they were less likely to back Mrs Clinton given Mr Comey's disclosure.
Sources close to the investigation have said the latest e-mails were discovered as part of a separate probe of former Democratic US Representative Anthony Weiner, the estranged husband of Clinton aide Huma Abedin.
Mr Weiner is the target of an FBI investigation into illicit text messages he is alleged to have sent to a 15-year-old girl in North Carolina.
Sources familiar with the matter said FBI agents working on the Weiner investigation saw material on a laptop belonging to Mr Weiner that led them to believe it might be relevant to the investigation of Mrs Clinton's e-mail practices.
"We never thought we were going to say thank you to Anthony Weiner," Mr Trump told the rally in Las Vegas at the Venetian, a hotel and casino on the famous Las Vegas Strip.
Mrs Clinton, who told a Florida rally on Saturday that Mr Comey's letter was "deeply troubling", did not address the issue directly on Sunday but referred vaguely to voters overcoming a"distraction".
"There's a lot of noise and distraction but it really comes down to the kind of future we want and who can get us there," she told a packed gay nightclub in Wilton Manors, Florida, where hundreds of supporters who could not get in lined the streets outside.
"We don't want a president who would appoint Supreme Court justices to overturn marriage equality," she said.