Two emails on the private account Hillary Clinton used as secretary of state were marked "Top Secret," a level of classification that is used for information whose disclosure is likely to "cause exceptionally grave damage to the national security."

The inspector general for the Intelligence Community discovered the messages on the server Clinton maintained at her New York home and notified senior members of Congress of the finding, the McClatchy Washington Bureau reported.

The FBI, meanwhile, is conducting an investigation into whether protected information was improperly stored on the Democratic presidential frontrunner's private server and a thumb drive held by her attorney, the newspaper group detailed.

The Clinton campaign said on Tuesday that the server was being turned over to the Justice Department, according to NBC News. Senate Judiciary Committee Chairman Chuck Grassley said the move was a "welcome development" but once again criticized the former seretary for her communications habits during her four-year tenure at Foggy Bottom.

"That's a long time for top secret classified information to be held by an unauthorized person outside of an approved, secure government facility," the Iowa Republican noted.

Clinton previously refused demands from critics to turn over the server to a third party, Fox News recalled. The presidential candidate has also defended her use of the private email account for government business, saying she opted for it as a matter of convenience and to limit the number of electronic devices she had to carry, the news channel recalled.

House Speaker John Boehner told NBC News that it was "about time" Clinton handed over the server. "Secretary Clinton's previous statements that she possessed no classified information were patently untrue," the Ohio Republican said. "Her mishandling of classified information must be fully investigated."

The State Department inspector general's office, meanwhile, told McClatchy that it was reviewing the use of "personal communications hardware and software" by Clinton's former top aides in compliance with requests from Congress. "We will follow the facts wherever they lead, to include former aides and associates, as appropriate," said Douglas Welty, a spokesman for the body.