The State Department said Friday it had no knowledge of what emails might have prompted the FBI to reopen it's investigation of Hillary Clinton and her private email server.

"We're just at the point here where we're trying to figure out what these emails pertain to, whether they're relevant to her time as secretary of state," State Department spokesman Mark Toner told reporters.

Toner said he didn't know much more than reporters and lawmakers did about the FBI's surprise decision, and said it had not received a letter from the FBI asking for more information. He said, however, that the State Department would cooperate with the FBI as it looks into the emails.

FBI Director James Comey notified Congress that the agency had "learned of the existence of emails that appear to be pertinent" to the previously-closed investigation of Clinton's use of a private email server during her tenure as head of the State Department. The new Clinton emails were found "in connection with an unrelated case."