Hillary Clinton's attorneys have given the FBI her private server and thumb drives contains thousands of emails, her campaign told reporters Tuesday night.

Emails exchanged on Clinton's private server contained "top secret" information, suggesting material housed on her personal email network were classified higher than previously known.

The State Department inspector general told lawmakers of the highly classified emails, which the watchdog uncovered as part of its continuing probe of the server and the top Clinton aides who used it, according to a report by McClatchy.

Among the four aides under investigation by the inspector general is Huma Abedin, Clinton's former deputy chief of staff and present campaign aide.

Abedin has yet to hand over all of her government-related communications, some of which were hosted on the private server reportedly housed in Clinton's Chappaqua home. She has provided just 338 pages of emails so far.

Clinton acknowledged the fact that Abedin held an account on her "clintonemail.com" domain Saturday in a sworn declaration submitted to a federal court.

The inspector general did not acknowledge who is included in its probe of four former State Department aides, but a number of them have handed over their personal emails to the agency.

Philippe Reines, Clinton's longtime spokesperson, reportedly provided 20 boxes of emails to the State Department upon request, and Cheryl Mills, Clinton's former chief of staff, stated through her attorney that she planned to hand over work-related emails Monday.

Mills' attorney did not return a request for comment on whether Mills followed through with the plan to submit emails Monday.

The inspector general's findings come as the closely-watched FBI investigation into the email arrangement raises further questions about the legality of Clinton's server.

Although the Clinton campaign has downplayed the criminal nature of the probe, FBI investigators are looking into whether those who established and used the private server mishandled classified information, which is a federal crime. Clinton's campaign said she "pledged to cooperate with the government's security inquiry, and if there are more questions, we will continue to address them."

The implications of the potentially illegal treatment of sensitive material are made more serious by the fact that top secret information was present on the server.

The inspector general found four classified emails among a sample of 40, and discovered two of those classified documents contained top secret information.