KABUL - Eight U.S. troops were killed and 14 wounded when a military helicopter crashed Sunday in southeastern Afghanistan after reporting engine failure, the U.S.-led coalition said in a statement.

The CH-47 Chinook helicopter was carrying 22 passengers and had a "sudden, unexplained loss of power and control and crashed," the statement said.

"It was not enemy fire related," said Col. Tom Collins, spokesman for NATO's International Security Assistance Force. "The pilot was able to radio in that he was having engine problems. We're confident it was not due to enemy action."

The helicopter crashed in the Shahjoi district of Zabul province, about 50 yards from the main highway between Kabul and Kandahar, and appeared to be destroyed and scattered in several pieces.

U.S. and Afghan military blocked reporters from entering the crash site.

The incident Sunday was the first U.S. military helicopter crash since May 2006, when a CH-47 Chinook helicopter that attempted a nighttime landing on a small mountaintop crashed in eastern Kunar province, killing 10 U.S. soldiers.

In 2005, a U.S. helicopter crashed in Kunar after apparently being hit by a rocket-propelled grenade, killing 16 American troops.

The military relies heavily on helicopters for transport and operations because of Afghanistan's forbidding terrain and lack of passable roads. Dust and high altitude of Afghan's mountains take a heavy toll on helicopter engines.

Thousands of U.S. forces are deployed in southeastern Afghanistan.