JOINT BASE ELMENDORF-RICHARDSON, Alaska (AP) — The U.S. Army says three soldiers have been killed and another has been injured after two helicopters collided and crashed in Alaska while returning from a training flight. The Army says two soldiers died at the scene of Thursday’s crash and a third died on the way to a hospital in Fairbanks. The Army statement says a fourth soldier was being treated at a hospital for injuries. The names of those killed are being withheld until relatives can be notified. The AH-64 Apache helicopters were from Fort Wainwright, based near Fairbanks. Officials say the crash is under investigation, and more details will be released when they become available. As a result, the Army says it has grounded aviation units for training after deadly helicopter crashes in Alaska and Kentucky killed 12 in the past month. A U.S. Army team from Alabama has been making its way to the Alaska Interior to the investigate the midair collision between two AH-64 Apache helicopters. Three soldiers were killed and a fourth was injured Thursday. Much is still not publicly known about the crash in the remote interior of the state that’s 250 miles from Anchorage. Thursday’s deadly crash follows a crash last month in Kentucky that killed nine.