WASHINGTON -- Three senior State Department officials in charge of diplomatic security resigned Wednesday after an independent panel found “systematic failures” in leadership that contributed to security lapses in the deadly Sept. 11 attacks on U.S. posts in eastern Libya.

Members of the Accountability Review Board, appointed by Secretary of State Hillary Clinton in the aftermath of the deadly attacks, presented their findings to the Senate and House foreign relations committees in closed hearings, with top State Department officials scheduled to appear in open sessions Thursday to answer the report’s sharp criticisms of security conditions at the time of the siege that killed Ambassador Chris Stevens and three other Americans in Benghazi.

The report stopped short of deeming the lapses a dereliction of duty, which would’ve required proof of intentional misconduct, and instead blamed poor leadership of senior officials for leaving the Benghazi consulate a highly vulnerable target in a volatile city where other visiting diplomats already had shut down operations or taken more precautions.

“We did conclude that certain State Department bureau-level senior officials in critical positions of authority and responsibility in Washington demonstrated a lack of leadership and management ability appropriate for senior ranks in their responses to security concerns,” retired Adm. Michael Mullen, former chairman of the Joint Chiefs of Staff and deputy chairman of the review board, told reporters Wednesday.

Three of those officials resigned after the findings were made public: Eric Boswell, assistant secretary of state for diplomatic security; Charlene Lamb, deputy assistant secretary in charge of embassy security; and a third unidentified official with the Bureau of Near Eastern Affairs, according to a knowledgeable congressional official, who requested anonymity because of the sensitivity of the issue. The resignations were first reported by the Associated Press.

The State Department would neither confirm nor deny the resignations. At least one lawmaker on the foreign affairs committees, however, acknowledged the resignations in a statement on the review board’s findings.

“The report made strong recommendations regarding personnel who should be held accountable, and I am pleased that some individuals in positions of responsibility have resigned today,” said Sen. Marco Rubio, R-Fla., a member of the Senate Foreign Relations Committee. “However, such resignations are a small step toward addressing this issue, which can only be fully resolved by an open and transparent internal review of the State Department’s relevant policies, operations and procedures.”

The consulate in Benghazi, according to the review board’s report, had an inadequate number of security agents, a lack of protective equipment, and was overseen by officials who failed to appreciate and craft a response to the city’s rapidly deteriorating security situation. The Libyan militia that was assigned to protect U.S. convoys was on strike at the time of the attack, upset over wages and working hours.

While the report doesn’t fill in the gaps on what the Obama administration knew about the attacks and when – one of the most controversial points in the government’s handling of the aftermath – the panel did find that there was no anti-American demonstration preceding the attack, as senior officials once had insisted.