The State Department added in the letter to Grassley that five of Clinton's aides had also had their security clearance revoked.

Four of the names are redacted but one aide listed in the email is Cheryl Mills, who worked as Clinton's chief of staff.

"As we previously informed the committee, these individuals had been granted access to classified information through a request made by Secretary Clinton designating them as researchers," Faulkner added.

It wasn't immediately clear if the State Department had authorized Grassley to publicly release the letter.

Faulkner in the letter asked Grassley to "protect" it and said that they were not clearing it for release by giving the letter to the Senate Judiciary Committee.

The letter includes a note saying it was authorized for release by Grassley.