Hillary Clinton
Hillary Clinton Reuters

Democratic presidential candidate Hillary Clinton continues to be embroiled in controversy, as on Thursday the US State Department said it cannot find 15 work-related emails from Clinton's private server that were released this week by a committee probe of the 2012 Benghazi attacks.

The emails consist of a series of unverified intelligence reports passed to her when she was US Secretary of State by her longtime political confidant Sidney Blumenthal, officials told the Associated Press.

Clinton is under pressure for having used a private email server while in office in breach of federal regulations, in a move that potentially was used to hide sensitive correspondences that officials are required to document. Suspicions were raised higher when thousands of emails in the server were wiped by Clinton.

She had claimed in March that all work emails from her personal server were given to the State Department, a claim proven false by the new revelation that shows she wiped out work emails as well.

The emails were only revealed during a probe of the Benghazi attacks, in which the American ambassador to Libya and three others were murdered. Critics allege the White House bungled handling of the attack.

In a testimony in 2013, Clinton said she took responsibility for the September 11, 2012 attack and cited a "personal" commitment to improving security provisions for US diplomatic missions overseas. She has been accused of purposely preventing the public release of details pertaining to the attack.

Speaking about the revelation of the 15 deleted work emails, Representative Trey Gowdy (R-SC) told Fox News on Thursday that the finding was "significant and troubling."

"This confirms doubts about the completeness of Clinton’s self-selected public record and raises serious questions about her decision to erase her personal server - especially before it could be analyzed by an independent, neutral third party arbiter," Gowdy said.

He added that the 15 erased emails revealed by the probe show Clinton "was soliciting and regularly corresponding with Sidney Blumenthal - who was passing unvetted intelligence information about Libya from a source with a financial interest in the country. It just so happens these emails directly contradict her public statement that the messages from Blumenthal were unsolicited."