WASHINGTON (AP) — Congress’ multiple investigations of the deadly 2012 attack on the U.S. diplomatic mission in Benghazi, Libya, have cost the Pentagon millions of dollars and thousands of hours of personnel time, according to the department.

In a March 11 letter, the Pentagon outlined its cooperation with six investigations of the Sept. 11 assault that killed four Americans, including U.S. Ambassador Chris Stevens, and its response to repetitive requests for information from about 50 congressional hearings, briefings and interviews.