The new emails being investigated by the FBI’s probe of Hillary Clinton’s use of a private computer server were reportedly uncovered after it seized electronic devices belonging to aide Huma Abedin and her husband, Anthony Weiner.
The New York Times said on Friday that law enforcement officials had revealed it was the seizure of the devices, and the discovery of emails that were previously not part of the FBI investigation, that had triggered the bureau’s announcement.
The FBI informed Congress on Friday it was investigating whether there was classified information in the new emails. The FBI said in July that its investigation was finished.
However, reports said the emails were not from the former secretary of state’s private device, but from those belonging to her top aide and her ex-husband. Mr Weiner is being investigated amid allegations he sent sexual messages to a 15-year-old girl.
The Associated Press said that in his letter to congressional leaders, FBI Director James Comey said the new emails that had come to light recently had prompted investigators to reopen its probe.
In his letter, Mr Comey, said that emails had surfaced in an unrelated case - now said to be the investigation into Mr Wiener’s alleged sexting - and that they “appear to be pertinent to the investigation”.
State Department spokesman Mark Toner said the department learned about the FBI letter from news reports and did not get any notification from the FBI. Toner pledged the department would “cooperate to the full extent that we can.”
The White House, through a spokesman, also declined to immediately comment.
Within minutes of the news, however, Republican presidential nominee Donald Trump seized on the development.
“Perhaps finally justice will be done,” Mr Trump said, at a rally in New Hampshire. He claimed the scandal was “bigger than Watergate”.
A yearlong investigation by the FBI that was concluded in the summer, focused on whether Ms Clinton sent or received classified information using the private server located in the basement of her New York home, which was not authorised to handle such messages.
Mr Comey said in July that his agents did not find evidence to support any criminal charges or direct evidence that Ms Clinton’s private server was hacked. He suggested that hackers working for a foreign government may have been so sophisticated they wouldn't have left behind any evidence of a break-in.
