In an exclusive interview with NBC News, Marcel Lehel Lazar, the hacker known as Guccifer, revealed that he was able to gain access to the completely unsecured server of former Secretary of State Hillary Clinton.

In another exclusive interview with Fox News, Lazar admitted that he easily and repeatedly breached the personal email server of Clinton in early 2013.

Last month, Lazar was extradited from Romania to the United States as he faces charges for hacking the email accounts of high-profile political figures, including Clinton, her former adviser Sidney Blumenthal, a member of the Bush family, and Gen. Colin Powell.

In the interview with Fox News, Lazar said that he first breached the AOL account of Blumenthal, and then used that as a springboard to infiltrate the personal server of Clinton. However, he did not see anything interesting at the time.

Clinton's server was said to contain almost 2,200 emails, with information that is now considered classified. There were also 22 emails that were tagged as "top secret" files.

Lazar also mentioned that he saw signs that there were other people on Clinton's server, possibly having broken into it as well.

A source told NBC News that investigators will be questioning Lazar regarding his alleged breach of Clinton's server. A review by the FBI revealed no signs of hacking attempts, and Lazar himself could not provide any proof to substantiate his claim of breaching the email account.

"There is absolutely no basis to believe the claims made by this criminal from his prison cell," said Brian Fallon, the national press secretary for Clinton's ongoing presidential campaign.

Fallon noted that, in addition to no proof being presented by Lazar, his descriptions of Clinton's server were inaccurate, and that it is unthinkable for the hacker to have not leaked the contents of the email account if he really did breach it, like what he did to his other targets.

Lazar is facing trial on Sept. 12 in the Eastern District of Virginia, where he has pleaded not guilty on nine counts of federal indictment for hacking crimes.