Hillary Clinton is asking the FBI to release any information it has about newly discovered emails that it says may be linked to her private server.

"If they're going to be sending this kind of letter that is only going to Republican members of the House, they need to share whatever facts they claim to have with the American people."

At a short news conference Friday evening, Clinton said no one in her campaign had been contacted by the FBI.

"It's imperative the bureau explain this issue in question, whatever it is, without any delay," she said.

When asked if she knew what information the FBI was referring to, Clinton told reporters, "Your guess is as good as mine."

Friday afternoon, FBI informed Congress it was investigating whether there is classified information in new emails that have emerged in its probe of Clinton's private server. The FBI said in July its investigation was finished.

The new emails came from a sexting investigation of Anthony Weiner, a U.S. official said, speaking only on condition of anonymity because the person was not authorized to comment publicly.

Weiner, a Democrat from New York City, quit Congress in 2011 after it was discovered that he was sending women sexually explicit messages. Weiner ran for mayor of New York in 2013, but that bid collapsed after it was reported that he was continuing to sext women

Weiner's estranged wife, Huma Abedin, is a longtime Clinton aide who now is a top official on her campaign team.

Federal authorities in New York and North Carolina are investigating online communications between Weiner and a 15-year-old girl. The U.S. official was familiar with the investigation but was not authorized to discuss the matter by name and spoke on condition of anonymity.

The disclosure, in a letter from FBI Director James Comey, came just 11 days before the presidential election and thrust a political liability back into the headlines that Clinton's campaign thought had been resolved and begun to recede from the minds of voters. The FBI couldn't guarantee its investigation would be finished before election day.

FBI letter offers little detail

Comey said the new emails prompted investigators to take another look at whether classified information had been mishandled, which had been the focus of its criminal investigation into Clinton's use of a private email server.

Comey didn't release any details about the emails. Initial reports were that there were new emails involving Clinton, which may not be the case.

"In connection with an unrelated case, the FBI has learned of the existence of emails that appear to be pertinent to the investigation," Comey wrote. "I agreed that the FBI should take appropriate investigative steps designed to allow investigators to review these emails to determine whether they contain classified information, as well as to assess their importance to our investigation."

Comey stressed in his letter that the FBI could not yet assess "whether or not this material may be significant," or how long it might take to run down the new investigative leads.

A U.S. official told The Associated Press on Friday that the newly discovered emails emerged very recently and did not come from Clinton's private server. The official spoke on condition of anonymity because this person was not authorized to discuss details publicly.

It was unclear what the emails contained, who sent them, or what connection they might have to the yearlong investigation the FBI closed in July without recommending criminal charges. The FBI probe focused on whether Clinton sent or received classified information using a server in the basement of her New York home, which was not authorized to handle such messages.

Comey said in July that his agents didn't find evidence to support a criminal prosecution or direct evidence that Clinton's private server was hacked.

U.S. Democratic presidential nominee Hillary Clinton is calling on the FBI to release any information is has about emails it says may be linked to her private server. (Carlos Barria/Reuters)

Clinton campaign calls for 'more information'

John Podesta, chairman of the Clinton campaign, released a statement asking for more transparency in the investigation.

"FBI director Comey should immediately provide the American public more information than is contained in the letter he sent to eight Republican committee chairmen," Podesta said.

"Already we have seen characterizations that the FBI is 'reopening' an investigation but Comey's words do not match that characterization. Director Comey's letter refers to emails that have come to light in an unrelated case, but we have no idea what those emails are and the director himself notes they may not even be significant."

It is extraordinary that we would see something like this just 11 days out from a presidential election."

Statement from <a href="https://twitter.com/johnpodesta">@johnpodesta</a> in response to Comey letter to GOP chairmen <a href="https://t.co/egyUMl68ZC">pic.twitter.com/egyUMl68ZC</a> —@brianefallon

Asked about Comey's letter during a campaign stop in Florida, Democratic vice presidential nominee Tim Kaine said he's "got to read a little more" before responding.

Comey, who has talked often about the FBI's need to be accountable to the public, promised extraordinary transparency about the investigation and during intervening months has authorized the release of investigative files from the case, which are normally kept confidential.

Open to criticism

That stance also left Comey, a career federal prosecutor who has served under both Republican and Democratic administrations, open to criticism from leaders in both parties that he was trying to influence the outcome of the presidential race.

Clinton campaign surrogates were already suggesting Friday that the FBI director was putting a thumb on the scale. Had he waited until after Nov. 8 to announce the discovery of the new emails, however, Comey would surely have faced criticism for sitting on major news until after the new president had been selected.

Republicans immediately pounced on the news, hoping to shake up a presidential race where most polls appear to show Republican nominee Donald Trump lagging well behind Clinton.

House Speaker Paul Ryan said Clinton has "nobody but herself to blame."

Speaking to cheering supporters at a rally in New Hampshire, Trump used Comey's new letter to attack Clinton.

"We must not let her take her criminal scheme into the Oval Office," said Trump, who has pledged to "lock up" his political rival if elected. "Perhaps finally justice will be done."