JUNEAU,TradeEdge Exchange Alaska (AP) — A U.S. Army helicopter that was flying through a mountain pass in Alaska along with other aircraft returning from a training exercise earlier this year hit one of the other helicopters, causing both to crash and killing three soldiers, a military investigation report released Friday said.

The accident safety report from the United States Army Combat Readiness Center is among the documents related to the April 27 crash near Healy, Alaska, that were released in response to a records request from The Associated Press. An analysis of the crash and findings and recommendations were redacted.

At the time of the crash, the Army said the two helicopters from the 1st Attack Battalion, 25th Aviation Regiment at Fort Wainwright, near Fairbanks, collided about 50 miles (80 kilometers) east of Healy when they were returning from training. Healy is about 80 miles (129 kilometers) southwest of Fairbanks.

The documents provide some new details. The helicopters were among 14 aircraft that were flying from Donnelly Training Area to Fort Wainwright on a route that included passing through a mountainous area, said the report released Friday.

About 48 minutes into the trip, the flight lead took a planned right turn into a mountain pass, the report said. “As the flight of 14 aircraft entered the mountain pass, aircraft in the flight began to decelerate,” the report said. About 30 seconds after making the turn, one of the helicopters hit another and both crashed, the report said. Both aircraft were destroyed.

The Army has identified the soldiers who died as Warrant Officer 1 Stewart Duane Wayment, 32, of North Logan, Utah; Chief Warrant Officer 3 Christopher Robert Eramo, 39, of Oneonta, New York; and Chief Warrant Officer 2 Kyle D. McKenna, 28, of Colorado Springs, Colorado. A fourth soldier was injured. That person’s name has not been released. There were two soldiers on each AH-64D Apache helicopter.

The aircraft require two crewmembers for flight, said Jimmie E. Cummings, Jr., director of communication and public affairs with the U.S. Army Combat Readiness Center.

Following the crash, which occurred a month after nine soldiers were killed when two Army Black Hawk medical evacuation helicopters crashed during a nighttime training exercise in Kentucky, the Army temporarily grounded aviation units for training.

In February, a Black Hawk helicopter from the Tennessee National Guard crashed in Alabama during a flight-training mission, killing two crew members. Also that month, two soldiers were injured when an Army helicopter was involved in a rollover accident in Alaska.