The US military failed to protect four Americans who died in attacks on a US compound in the Libyan city of Benghazi, says a Congressional report.
The Obama administration was criticised for lax security and a slow response to the 2012 attacks on a US compound, in the report by House Republicans.
But they found no new evidence of wrongdoing by ex-Secretary of State and White House hopeful Hillary Clinton.
The issue has long haunted her on the campaign trail.
Islamic militants stormed the US compound in the Libyan city of Benghazi in 2012, killing four Americans including ambassador Chris Stevens.
Earlier this year, Mrs Clinton said she took responsibility for the attack during an 11-hour hearing before the House Republicans committee on the matter.
Military leaders have said they did not have sufficient intelligence on what was happening or the resources to respond quickly enough.
In announcing the conclusion of the committee’s investigation, chairman Trey Gowdy, a Republican from South Carolina, said: “Nothing was en route to Libya at the time the last two Americans were killed almost eight hours after the attacks began.”
US help was too slow because of “an obsession with hurting the Libyans’ feelings,” he said.
The report has “not found anything to contradict the conclusions of multiple, earlier investigations,” Mrs Clinton’s campaign said in a statement.
Democrats, in their own report, said the State Department’s security measures were “woefully inadequate” but Mrs Clinton had never refused requests for more security.
They called the Republicans’ report a “conspiracy theory on steroids, bringing back long-debunked allegations with no credible evidence whatsoever.”
They accused the committee’s Republican majority of targeting Mrs Clinton but Mr Gowdy said that was never the committee’s aim.