Washington CNN  — 

The State Department has not been able to find emails from former Secretary of State Hillary Clinton’s private server in its archives, State Department officials said Thursday.

The officials said the State Department is missing all or part of 15 emails from longtime confidant Sidney Blumenthal released this week by a House panel investigating the 2012 attack on the U.S. diplomatic facility in Benghazi, Libya. Blumenthal provided the Select Committee on Benghazi with the emails.

“She has turned over 55,000 pages of materials to the State Department, including all emails in her possession from Mr. Blumenthal,” said Clinton spokesman Nick Merrill on Thursday.

Officials said the exchanges with Blumenthal were not among the 55,000 pages of emails Clinton handed over to the State Department, even though Clinton insisted she gave her former agency all of her work-related correspondence from private account during her time at State.

“We have confirmed that the emails Secretary Clinton provided the department include almost all of the material in Mr. Blumenthal’s production,” one of the officials said. “There here 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.”

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But the official added, “The substance of those 15 emails is not relevant to the 2012 attacks in Benghazi.”

Rep. Trey Gowdy, chairman of the committee, has petitioned Clinton and her former aides to reveal what they know about the attack at an American diplomatic compound that killed four Americans. Gowdy’s recent attention has turned to any emails between Clinton and Blumenthal.

Gowdy’s committee has located emails between the pair and has asked the State Department to turn over their copies of the correspondence, which it said it did Thursday in a letter to the committee.

“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.”

A Clinton aide says they do not recognize many of the materials Blumenthal turned over to the committee and cannot speak to their origin.

They do not, the aide said, have a record of other correspondence between her and Mr. Blumenthal beyond that which they turned over to the State Department.

The aide also said that Clinton turned over all emails from Blumenthal, including more than a dozen emails that were not included in what he handed over to the House committee.

The missing emails are likely to fuel Republican charges that Clinton is hiding emails from her private server. The committee believes almost half of Clinton’s public record on the attacks can be uncovered by looking at her emails with Blumenthal.

Gowdy’s committee released 179 pages of emails on Monday. The emails that Blumenthal produced in response to the committee’s request numbered about 120 pages.

Clinton has said that the emails she received were “unsolicited,” but the committee believes the new emails show that not to be the case.

Blumenthal met behind closed doors last week with the committee for nearly nine hours about amid revelations he sent Clinton more than two dozen memos that read like intelligence reports. The emails have drawn Republican scrutiny because Blumenthal sent them while advising businesses interests in Libya and working with the Clinton Foundation, although Blumenthal said his work for the Clinton Foundation had “nothing whatsoever to do with my emails to my friend.”

Democrats complained that the committee has drifted from its mission of investigating the attacks in Benghazi and has become an inquest into Clinton, the frontrunner for the Democratic presidential nomination.

CNN’s Chris Frates and Dan Merica contributed to this report.