WASHINGTON — The State Department said Thursday that the new trove of documents it has provided Congress from its own investigation into the deadly 2012 attack on U.S. diplomatic facilities in Benghazi, Libya, do not change the “essential facts” known about the attack.

The facts set out by the State Department’s Accountability Review Board report, released in December 2012, did not find former Secretary of State Hillary Clinton — now a Democratic presidential candidate — responsible for security lapses in Benghazi.

But the report concluded that the U.S. mission in Benghazi was unprepared for the attack, and outlined widespread failings within the State Department while Clinton was in charge.

Four Americans, including U.S. Ambassador Chris Stevens, were killed when militants stormed U.S. facilities in the eastern Libyan city of Benghazi on the night of Sept. 11, 2012.

U.S. Rep. Trey Gowdy, R-South Carolina, who heads the House Select Committee on Benghazi, said earlier Thursday that the State Department had given his panel some 4,000 pages from its 2012 Accountability Review Board probe into Benghazi. He said it was the first time State Department had handed Congress papers from an Accountability Review Board, special panels that State Department sets up to investigate attacks on U.S. diplomatic facilities.

A State Department letter to Gowdy reviewed by Reuters last week made clear the department was unhappy about relinquishing the Accountability Review Board files, saying it worried “the prospect of congressional scrutiny could have a chilling effect” on future Accountability Review Boards.

“I’m not going to characterize the contents of the documents that were provided, except to say that they don’t change the essential facts that have been known since the accountability review board report came out,” State Department spokeswoman Marie Harf said on Thursday.

A Democratic aide to the Benghazi committee went further, saying the Accountability Review Board papers “identified no evidence to support claims that Secretary Clinton ordered a stand-down, personally denied security requests, oversaw a covert weapons program, or any of the other wild claims Republicans have been making for months.”

Republicans say the State Department under Clinton failed to protect diplomatic personnel in Benghazi. Democrats say the panel’s efforts are politically motivated to undercut Clinton’s 2016 presidential candidacy.

The State Department has already turned over thousands of pages of other documents to Gowdy’s panel. The House committee is also investigating Clinton’s use of a private email server and plans to have her testify.