Despite claims to the contrary, former Secretary of State Hillary Clinton failed to turn over all work-related emails she sent from her private home email server during her tenure, the State Department revealed Thursday.

Officials said the State Department couldn't find all or part of 15 emails sent between Clinton and longtime political confidant Sidney Blumenthal, who last week surrendered the emails after being subpoenaed by the House committee investigating the 2012 attacks in Benghazi, reported The Associated Press.

The emails were sent before the Sept. 11 attack on the U.S. diplomatic compound and consist of intelligence reports passed on to Clinton by Blumenthal, according to AP. He did not work for the department, yet Clinton regularly sent intelligence reports on Libya, which she sometimes forwarded to colleagues.

"We have confirmed that the emails Secretary Clinton provided the Department include almost all of the material in Mr. Blumenthal's production," a department official said on condition of anonymity, reported the National Journal. "There are, however, a limited number of instances - 15 - in which we could not locate all or part of the content of a document from his production within the tens of thousands of emails she gave us."

Clinton insisted that she gave the State Department over 30,000 of her work-related correspondence as secretary of state, which were stored on her personal server despite rules and said she deleted about the same number of emails from her private server, which she said "were private, personal" messages about her mother's funeral, her daughter's wedding, yoga and family vacations.

When asked about the discrepancy, Nick Merrill, a Clinton campaign spokesman, told AP, "She has turned over 55,000 pages of materials to the State Department, including all emails in her possession from Mr. Blumenthal."

The missing emails include various reports on politics among Libyan rebel groups, media accounts about the killing of one of the sons of Libyan leader Moammar Gadhafi, and news of a former Gadhafi minister's assassination.

AP said that Clinton's responses are usually short, and none of the emails focus particularly on Benghazi. In an August 2011 message, Clinton told Blumenthal she will be meeting rebel leaders in Paris the next day and says she had "to resort to new iPad" because Hurricane Irene knocked out her electricity and Blackberry coverage. In another from March 2012, Clinton relayed an adviser's skepticism of one of Blumenthal's reports about post-Gadhafi Libya. "This strain credulity based on what I know. Any other info about it?" Clinton wrote, according to AP.

Blumenthal sent Clinton a long note in August 2012 discussing Libya's new interim President Mohamed Yousef el-Magariaf, to which she responded: "Another keeper - thanks and please keep 'em coming." She responded to a follow-up report four days later, saying, "Fascinating. I had a very good call w him."

The State Department told the Benghazi committee on Thursday that they have lost confidence in Clinton and can no longer be sure that she turned over all work-related emails, according to officials who spoke to AP on the condition of anonymity.

Rep. Trey Gowdy, chairman of the committee, has suggested that Clinton purposefully deleted work-related emails to hide evidence surrounding the Benghazi attacks.

"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 in a statement on Thursday. "This has implications far beyond Libya, Benghazi and our committee's work. This conclusively shows her email arrangement with herself, which was then vetted by her own lawyers, has resulted in an incomplete public record."

Blumenthal, who was barred from working at the State Department, was receiving $10,000 a month pay from the Clinton Foundation while providing intelligence reports to Clinton, but says his work at the foundation had "nothing whatsoever to do with my emails to my friend," and Clinton has insisted his advice was "unsolicited."

"These new messages in many instances were Clinton's responses, which clearly show she 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," the panel statement says. "It just so happens these emails directly contradict her public statement that the messages from Blumenthal were unsolicited."

He was also advising friends who were working on new business ventures in Libya that would profit from the transitional government. One of those partners was reportedly the author of the intelligence memos Blumenthal sent to Clinton, reported Politico.