New emails related to Hillary Clinton that FBI Director James Comey said prompted further investigation were found as part of an ongoing investigation into former U.S. Rep. Anthony Weiner, NBC News and the Associated Press reported.
Law enforcement agencies have been examining online communications between Weiner, the estranged husband of Clinton aide Huma Abedin, and a 15-year-old girl.
NBC News and the AP reported the link to the Weiner case citing unnamed officials.
The emails were found on a laptop that Weiner allegedly used to send inappropriate text messages and pictures to an underage girl, sources told NBC News.
Investigators also discovered Abedin had used the same laptop to send emails to Clinton and now they are checking those messages to see if there was any classified information on them, the sources said.
Asked at a Friday news conference about the email probe's link to Weiner, Clinton said: "You know, we've heard these rumors, we don't know what to believe."
The FBI informed Congress on Friday it is 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 disclosure, in a letter from 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.
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.
Donald Trump on Friday seized on the FBI's decision to investigate new messages connected to Hillary Clinton's emails.
Trump opened his rally in Maine by saying he has "great respect for the FBI for righting this wrong."
He said the "the American people fully understand her corruption" and he hopes "justice will finally be served."
Trump, however, did not immediately mention Weiner.
Federal authorities began investigating the former New York congressman in late September after an online news outlet, DailyMail.com, published an interview with a 15-year-old North Carolina girl who said she had exchanged sexually explicit messages with him over several months.
Among other things, the girl said that during a Skype chat, Weiner had asked her to undress and touch herself.
Weiner released a statement acknowledging that he'd corresponded with the girl. In it, he apologized, saying he had "repeatedly demonstrated terrible judgment about the people I have communicated with online."
But he also said he had "likely been the subject of a hoax" and provided an email, written by the girl to a teacher, in which she recanted her story.
Federal prosecutors in both North Carolina and New York were initially involved in the investigation, but agents in New York subsequently took the lead, according to a spokeswoman for the U.S. attorney for the Western District of North Carolina.
Weiner resigned from Congress in 2011 after it was revealed he had been exchanging sexually explicit messages with multiple women. Abedin announced their separation in August following new sexting revelations.