Rep. Trey Gowdy, chairman of the House Select Committee on Benghazi, released an email Sunday from a former adviser to Hillary Clinton after the CIA cleared the document for release late Saturday evening.

The email, which was sent to Clinton by Sidney Blumenthal, a close confidante, indicates the former secretary of State forwarded a memo that contained the identity of a CIA source.

"[T]he name of the alleged source was redacted from the material cleared for public release by someone in the Executive Branch – the fact that the CIA says it didn't do it does not mean the material was not sensitive or classified," Gowdy wrote in a letter Sunday to Rep. Elijah Cummings, the select committee's top Democrat. "And in fact, additional information remains in the document that ordinarily would be considered highly sensitive. This appears to mean either Mr. Blumenthal conveyed false and unreliable information to Secretary Clinton about Libya and misrepresented it, or the review process is faulty or has been politicized."

The email in question discussed the apparent surprise Muammar Gadhafi, then the dictator of Libya, felt after the United Nations authorized the use of force against Gadhafi's troops. Blumenthal told Clinton that Gadhafi had dispatched representatives to Syria and Yemen in an effort to encourage the Arab League to stay out of Western-driven attacks on Libya.

Gowdy also used his letter to argue that the committee's work, far from being focused on Clinton, has seen 54 witnesses appear before the panel, only one of whom was asked extensively about Clinton's private email use.

That witness, Bryan Pagliano, quickly invoked Fifth Amendment rights and declined to answer questions.

"[A]fter the media — not our committee, but the media — broke the news of her exclusive use of private email and her use of a personal server in early March of 2015, the next 21 witness interviews in a row had nothing to do with Clinton or her email," Gowdy noted.

His committee has been under fire after House Majority Leader Kevin McCarthy said the Benghazi investigation had an active role in bringing down Clinton's poll numbers, which Democrats said showed the purpose of the committee was to hurt Clinton.

Gowdy, who has worked since the committee's formation in May 2014 to keep details of the probe under wraps to avoid the spotlight, has seen Democrats and even at least one fellow Republican tear down the select committee's probe on the grounds that it is driven by partisan motivations. Those criticisms have intensified as Clinton prepares to appear before the committee for a highly-anticipated hearing Thursday.

Gowdy told GOP members to "shut up talking about things that you don't know anything about" in appearance Sunday on CBS' "Face the Nation."

The South Carolina Republican has repeatedly defended the integrity of the committee's work, arguing there is no evidence to support accusations of politicization in the probe.