The FBI informed Congress on Friday it is investigating whether there is classified information in new emails that have emerged in its probe of Hillary Clinton's private server. The FBI said in July its investigation was finished.
The disclosure raises the possibility of the FBI reopening the criminal investigation involving the Democratic presidential nominee just days before the election, although it is not clear if that will happen.
Clinton's campaign didn't immediately respond to request for comment.
In a letter sent to congressional leaders, FBI Director James Comey says that new emails have come to light recently that have prompted investigators to take another look at the sensitive government information that flowed through the private email sever Clinton used while serving as secretary of state.
It was not clear from Comey's letter where the new emails came from or who sent or received them.
Rep. Bob Goodlatte, the Republican chairman of the House Judiciary Committee, said the FBI's decision reinforces the committee's view that the more that is learned about the server, "the clearer it becomes that she and her associates committed wrongdoing and jeopardized national security."
A yearlong investigation by the FBI focused on whether Clinton sent or received classified information using the private server located 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 any criminal charges or direct evidence that 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.