An American military helicopter crashed Thursday near the city of Qaim in western Iraq, killing some of the seven service members aboard, United States officials said.
It was unclear why the aircraft, an HH-60 Pave Hawk, went down, the officials added. They did not rule out ground fire, and they could not confirm how many people had been killed.
One official said the helicopter was not on a combat operation but was ferrying troops.
Maj. Adrian J. Rankine-Galloway, a Pentagon spokesman, said Thursday night that rescue personnel had been deployed and that the crash, in Anbar Province, near Syria, was under investigation.
Ahmed al-Mahilawi, the mayor of Qaim, said that the helicopter crashed about 20 miles southeast of the town center, near a phosphate factory and railway station. The American military uses a base in the area.
Local residents reported that the helicopter crashed shortly after takeoff, Mr. Mahilawi said in a telephone interview.
Coalition forces have sealed off the area of the crash, he said, adding that preliminary indications were that the helicopter had a technical malfunction. He did not have any information on fatalities or the number of people on board.
The HH-60 is a modified version of the Black Hawk helicopter. It is often flown by the Air Force for medical evacuation missions, and is used by Special Operations pararescue specialists.
The crash comes as American forces and their Iraqi counterparts are winding down combat operations against the Islamic State. In December, the Pentagon said there were roughly 5,200 American troops still in the country.
The border between Iraq and Syria still poses a critical threat to the American-led coalition battling the Islamic State.
While the extremist group has been pushed from all of the urban centers it once controlled in Iraq, fighters have escaped and are now hiding in the vast desert along the border. Iraqi security forces conduct weekly operations to try to clear the area of militants.
American forces operate from two Iraqi bases in the western part of the country: one outside Qaim and the larger, established Asad air base, which is used as the logistics center and resupply hub for Qaim.
American forces do not routinely conduct their own missions on Iraqi soil, according to American military and coalition officials. Instead, they provide surveillance, intelligence and air support to Iraqi-led missions.