Updated

The Pentagon says Congress' multiple investigations of the deadly 2012 attack on the U.S. diplomatic mission in Benghazi, Libya, have cost the department millions of dollars and thousands of hours of personnel time.

In a March 11 letter, the Pentagon described repetitive requests for information from about 50 congressional hearings, briefings and interviews. The department was responding to a Feb. 4 letter from Rep. Adam Smith of Washington state, the top Democrat on the House Armed Services Committee.

The Sept. 11 assault killed four Americans, including U.S. Ambassador Chris Stevens. An independent review and bipartisan Senate Intelligence committee report have mainly faulted the State Department and the security at the mission.

Smith, in a subsequent letter to the committee's Republican chairman, complained about the financial strain on the military.