NATO: Troops in crash were after Taliban leader

The U.S.-led coalition says that the 30 U.S. troops and seven Afghan soldiers who died in a weekend helicopter crash in eastern Afghanistan were on a mission targeting a Taliban leader.

In a statement released Monday evening, NATO said an insurgent with a rocket-propelled grenade reportedly fired on the chopper, which was transporting the U.S. and Afghan troops to the scene of an ongoing fight between coalition forces and insurgents.

NATO says the operation began as a search for a Taliban leader responsible for insurgent operations in the Tangi Valley of Wardak province. The coalition says the ground forces saw several insurgents armed with rocket-propelled grenade launchers and AK-47s and called for assistance.

The helicopter crashed as it was arriving to assist.

German Brig. Gen. Carsten Jacobson, a spokesman for the U.S.-led coalition, told reporters that troops had secured the crash site in a rugged area of eastern Wardak province and nobody was being allowed in or out of the area while the investigation was ongoing.

Jacobson said the coalition still had not yet determined the exact cause of the crash, but some officials have said the heavy and lumbering transport helicopter was apparently shot down. Officials said the helicopter was hit as it was flying in and approaching the area.

"We are still investigating this incident so we have no picture of what was the cause for the incident. That is what the investigation is basically all about," Jacobson said.

The helicopter was ferrying a group of Navy SEALs to reinforce a group of Army Rangers who were under fire. It remains unclear if the Rangers and SEALs were taking part in a night raid to capture or kill an insurgent leader.

It was deadliest single loss for U.S. forces in the decade-long war.