Updated

House Democrats on Wednesday demanded an end to a Republican-led investigation into the deadly attack on the U.S. diplomatic mission in Benghazi, Libya, calling the probe a partisan "witch hunt."

Reps. Adam Smith of Washington state, the top Democrat on the House Armed Services Committee, and Elijah Cummings of Maryland, the top Democrat on the House Oversight and Government Reform Committee, said the multiple inquires and reports have answered the questions surrounding the Sept. 11, 2012, assault.

Four Americans, including U.S. Ambassador Chris Stevens, were killed.

Nineteen months after the attack, Republicans are throwing "as much mud against the wall in hope something sticks," Smith said. "It is time to get past the Benghazi witch hunt."

Republicans, who control the House, insist there are unresolved issues and they have a responsibility to fulfill their oversight role, a point underscored by Speaker John Boehner, R-Ohio, this week.

Cummings and Smith spoke shortly before the House committees planned to interview retired Army Gen. Carter Ham, who headed U.S. Africa Command on the night of the attack.

Cummings said Ham has been interviewed at least six times, and that an independent report and a Republican report from the House Armed Services Committee found no evidence of a "stand down" order to the military, delaying a response. Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, told Congress last June that personnel in Tripoli were never told to "stand down" and top Republicans on the House Armed Services Committee reported in February that no such order was given.

The February interim report from the Republicans on the Armed Services Committee, including panel chairman Rep. Howard "Buck" McKeon, R-Calif., said Army Lt. Col. S.E. Gibson wanted to take three special operators from Tripoli to Benghazi after the first attack. Military commanders were concerned about the safety of Americans in the capital city, fearing a wave of attacks and the possibility of hostage taking.

Cummings said "this is the insulting way Republicans have conducted this investigation" and they are playing a "game of political gotcha with our military."

Multiple independent and congressional investigations have largely faulted the State Department for inadequate security at the mission.

Republicans have accused the Obama administration of trying to mislead the American people about an act of terrorism in the final weeks before the November election.