U.S. commanders on Sunday "ruled out" hostile fire as the cause of a military helicopter crash that killed 10 American soldiers during a combat operation in the rugged mountains of eastern Afghanistan.

The CH-47 Chinook crashed Friday night in a remote ravine inaccessible by road, but troops had been able to recover all the bodies, the military said.

The craft was operating from a mountaintop landing zone as part of a U.S. military offensive seeking Al Qaeda and Taliban militants near Afghanistan's border with Pakistan. But a U.S. military statement said that "enemy action was ruled out as a possible cause" of the crash.

Authorities said the dead were from Fort Drum, N.Y., home base of the Army's 10th Mountain Division. Their units and identities were being withheld pending notification of relatives, said Lt. Col. Paul M. Fitzpatrick, the division's chief public affairs officer.

About half of the roughly 18,000 U.S. military personnel in Afghanistan are from the 10th Mountain Division.

The crash was the deadliest for U.S. forces here in a year and comes at a time of increasing militant attacks and counter-operations by Afghan and foreign troops.

CountryWatch: Afghanistan

The helicopter went down in Kunar province, where 2,500 Afghan and Americans soldiers are conducting Operation Mountain Lion — one of the biggest offensives since U.S.-led forces ousted the hard-line Taliban regime for harboring Usama bin Laden and Al Qaeda bases.

Lt. Tamara D. Lawrence, a spokeswoman for the U.S.-led coalition, said an investigation team was at the crash site and the dead had been recovered.

"The area was inaccessible to trucks and vehicles, so helicopters were used to retrieve the bodies of the 10 soldiers from the ravine," Lawrence said. She did not know if the helicopter had been removed.

Fighting has been on the rise in Afghanistan's southern and eastern provinces, where militants have been using suicide and roadside bombs more than ever.

The 10 deaths brought to at least 25 the number of U.S. military personnel killed in Afghanistan this year, according to the Web site icasualties.org, which relies on Defense Department information.

At least 234 U.S. military personnel, including those killed Friday, have died in Afghanistan and neighboring Pakistan and Uzbekistan as a result of the conflict, according to Defense Department statistics.

Last June, all 16 soldiers 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.