KABUL, Afghanistan — A U.S. Black Hawk helicopter crashed in restive Kandahar province Thursday, killing seven American troops and four Afghans, U.S. and Afghan military officials said.

Afghan officials said the crash site was in Shah Wali Kot, a volatile district where insurgents have long been active.

The NATO force said the cause of the crash was under investigation, and was tight-lipped about whether insurgent fire had been reported in the area. Usually, the military makes a quick announcement if there is no indication the craft was brought down by enemy fire, and if factors such as weather or mechanical failure are suspected.

The Taliban claimed responsibility for bringing down the helicopter, but the group routinely boasts of shooting down any NATO aircraft that crashes. The Taliban and other militant groups have only rarely been able to bring down Western helicopters during the decade-old war, but manage to do so occasionally, often with significant fatalities.

A U.S. military officer in Afghanistan said it was possible the helicopter had been shot down.

“It’s conceivable. There were enemy in the area,” he said, speaking on the condition of anonymity because an investigation of the crash is under way. The Black Hawk burned when it crashed, making it more difficult to determine the cause.

Afghan fighters were seen moving toward the burning crash site but were driven off by another U.S. helicopter, the officer said. The bodies of those on board were recovered, he said.

The casualties included three U.S. special operations troops, four American crew members, three Afghan special operations soldiers and a civilian interpreter.

The war’s most lethal single incident for U.S. troops came a year ago when insurgents shot down a Chinook in Wardak province, killing all 38 aboard, including 30 Americans, many of whom were Navy SEALs.