The U.S. military says the Chinook helicopter crash in Afghanistan that killed 30 US troops in August was caused by a rocket-propelled grenade that struck the aircraft.
An official investigation report released Thursday found no wrongdoing by personnel involved in the August 6 mission.
The report dismissed speculation the helicopter had flown into a trap set by Taliban militants. It says the incident was the result of "the enemy being at a heightened state of alert" due to the three-and-a-half hour coalition air operation in the area.
The report said after the grenade hit the chopper's rotor blade the aircraft plummeted into a dry creek bed and was engulfed in flames.
Thirty U.S. troops, including members of the elite Navy SEALs, were killed along with seven Afghan soldiers and an Afghan interpreter in the crash in Tangi Valley in Wardak province. It was the worst loss of life for the United States in a single incident during the decade-long war in Afghanistan.
Some information for this report was provided by AP and AFP.