The U.S. Army has temporarily grounded all AH-64 Apache helicopter training flights after a crash near Fort Hood, Texas, killed two soldiers earlier this week. Army leaders ordered a temporary stand-down of Apache training flight operations following the deadly crash on Wednesday. The Army said the pause would remain in effect until officials have a better understanding of the accident’s root cause.

“The stand-down will remain in effect until we have a better understanding of the root cause of the accident,” the Army said in a statement.

Investigators from the Army Combat Readiness Center at Fort Rucker, Alabama, arrived at the crash site Thursday and will lead the investigation.

Chief Warrant Officer 2 Deontre Huey, 34, and Warrant Officer Seth Olmstead, 25, were killed in the crash, according to Fort Hood. Both soldiers were assigned to Bravo Company, 1st Battalion, 227th Aviation Regiment, 1st Air Cavalry Brigade, 1st Cavalry Division at Fort Hood.

“Our hearts and deepest condolences are with the families of the Soldiers we lost Wednesday,” Lt. Gen. Kevin Admiral, Fort Hood commanding general, said. “The Army is a family, and a tragedy like this is felt throughout our formations and our community.”

The AH-64 Apache is an attack helicopter designed for two crew members, with the pilot seated in the rear and the co-pilot and gunner in the front. The four-bladed aircraft can carry up to 16 Hellfire missiles, 76 aerial rockets and 1,200 rounds for its 30 mm gun.

The Army describes the AH-64E as a highly mobile and lethal aircraft capable of destroying armor, personnel and materiel targets in obscured battlefield conditions at ranges of up to 8 kilometers, or about 5 miles.

The Apache has been upgraded and modernized since it was first introduced in 1984 and is expected to remain in service until 2050. The Army’s temporary stand-down applies to Apache training flight operations while investigators work to determine what caused the Fort Hood crash.