KABUL, Afghanistan — All nine troops killed in the worst helicopter crash for the coalition in Afghanistan in four years were Americans, the Pentagon has confirmed without providing further information on why the aircraft carrying Navy special forces went down.

NATO said there were no reports of enemy fire in a rugged area in the Daychopan district of Zabul province, where Tuesday’s crash took place. But Taliban spokesman Qari Yousef Ahmadi told The Associated Press by telephone that insurgents shot down the helicopter.

The Taliban often exaggerate their claims and sometimes take credit for accidents.

The U.S. Defense Department released the identities of the troops late Wednesday, saying four were with the Navy special forces — three of them Navy SEALS — and the rest were soldiers.

Fort Campbell spokesman Rick Rzepka said that the five soldiers were assigned to the 101st Combat Aviation Brigade.

Tuesday’s crash was the deadliest since May 2006, when a Chinook helicopter went down while attempting a nighttime landing on a small mountaintop in eastern Kunar province, killing 10 U.S. troops.

Aircraft are used extensively in Afghanistan by both NATO and the Afghan government forces to transport and supply troops because the terrain is mountainous and roads are few and primitive.

Lacking shoulder-fired missiles and other anti-aircraft weapons, the Taliban rely mostly on machine guns and rocket-propelled grenades to fire at aircraft during takeoffs and landings.

Most helicopter crashes in the country have been accidents caused by maintenance problems or factors such as dust.

On Wednesday, NATO confirmed the capture of a Taliban commander operating in Marjah, the site of a major coalition offensive in February. The commander, who helped supply local militants, was captured during an Afghan and coalition operation in Helmand province Tuesday.

After questioning residents at the scene, troops detained the commander and two of his associates. Troops found 45 pounds (20 kilograms) of wet opium — that is, the gum collected from the plant before it is dried — which is often sold to fund the insurgency.

On Thursday, NATO raised the death toll from an insurgent attack on a joint Afghan army outpost in eastern Afghanistan near the Pakistan border, saying it left more than 30 of the militants dead.

Troops at the combat outpost in the Spera district of Khost province returned fire with mortars in that attack, which happened Tuesday, NATO said in a statement. Initial reports found there were no civilian casualties. There were no casualties among NATO or Afghan troops.

In the south, two civilians died and four were wounded Wednesday when an insurgent threw a hand grenade at a police car in Zaranj district of Nimroz province, said the deputy provincial police chief, Mohammad Mousa Rasooli. The grenade missed the car and exploded but hit those nearby.

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Associated Press Writer Mirwais Khan contributed to this report.