A U.S.-led coalition military transport helicopter crashed while conducting combat operations in the remote mountains of eastern Afghanistan, killing all 10 American soldiers on board, a U.S. military spokeswoman said Saturday.

The CH-47 Chinook crashed late Friday while on a mission in support of Operation Mountain Lion, an offensive to root out Taliban and Al Qaeda militants near the border with Pakistan. The crash was not the result of hostile fire, said Lt. Tamara D. Lawrence, a coalition spokeswoman.

"The remains of all the 10 soldiers have been found and there are no survivors," she told The Associated Press. "There is no indication that the helicopter came down due to some enemy action."

The soldiers were part of a more than 20,000-strong coalition force, mostly operating in the volatile south and east of Afghanistan. About 18,000 of those forces are American.

The helicopter was conducting "operations on a mountaintop landing zone" when it crashed near Asadabad in Kunar province, about 150 miles east of Kabul, the capital, the military said in a statement. Rescue and recovery operations began at daybreak Saturday, Lawrence said. An investigation into the crash is under way.

Some 2,500 Afghan and U.S. soldiers are conducting a joint military operation in Kunar, one of the biggest since the ouster of the hardline Taliban regime by U.S.-led forces in late 2001 for hosting Al Qaeda.

Asadabad is surrounded by rugged mountains, and a large U.S. military base there houses hundreds of troops.

The police chief of Kunar province, Gen. Abdul Ghafar, said the helicopter crashed about 10 miles northwest of the U.S. base in Asadabad. He said the crash was a day's walk from any passable road.

"The area of the crash is a mountainous area and it is difficult to reach," Ghafar said.

A military statement said that other aircraft and crews were near the landing zone during the crash and confirmed that the helicopter was not shot down. Lawrence said that although it was dark, the other coalition aircraft would have known if an enemy rocket had been fired.

The military did not say what unit the U.S. troops were from, only specifying that they were soldiers, meaning from the Army, and not Marines.

In September, a Chinook helicopter crashed in a mountainous area in southeastern province of Zabul, killing all five American crew members, and in June, all 16 troops on board a Chinook died in Kunar when it was hit by a militant's rocket-propelled grenade — the deadliest attack against American forces in Afghanistan.

In August, 17 Spanish troops died in a helicopter crash in the western city of Herat. That crash was blamed on fierce winds.

In April of last year, 15 U.S. service members and three American civilians were killed when their Chinook went down in a sandstorm while returning to the main U.S. base at Bagram.

At least 224 U.S. military personnel have died in Afghanistan, Pakistan and Uzbekistan as a result of the U.S. invasion of Afghanistan in late 2001. Of those, at least 141 were killed by hostile action.