A Schofield Barracks Black Hawk helicopter crashed in southern Afghanistan today, and at least some of the seven Americans on board who were killed were based out of Hawaii, sources said.

In addition to the Americans, four Afghans were killed.

Lt. Col. Derrick W. Cheng, a Schofield spokesman, said he could not confirm that the helicopter was based out of Hawaii.

“At this time I can’t release any of the information. We’re still awaiting the formal (family) notification process,” Cheng said.

U.S. officials said three of the seven American troops killed were special operations forces — two Navy SEALs and a Navy explosives expert. The officials spoke on condition of anonymity because they were not authorized to disclose the information.

Three members of the Afghan security forces and a Afghan civilian interpreter also were killed, said Jamie Graybeal, a spokesman for the coalition. 

NATO forces said they could not confirm what caused Thursday’s crash and stressed that it was still being investigated. The Black Hawk was operating in support of an ongoing assault on the ground but initial indications were that it was not shot down, according to U.S. officials who spoke anonymously because the investigation was continuing.

About 2,600 Hawaii soldiers with the 25th Combat Aviation Brigade, which includes Black Hawk helicopters, are in southern Afghanistan on a year-long deployment.

In April, four Schofield soldiers, among them Waipahu native Army Chief Warrant Officer 2 Don C. Viray, 25, were killed in a Black Hawk helicopter crash in southern Afghanistan.

The Kandahar provincial government said the helicopter was shot down in Shah Wali Kot district, a rural area north of Kandahar city where insurgents move freely and regularly launch attacks. Provincial spokesman Ahmad Jawed Faisal did not provide details or say how the province had confirmed the information.

The crash killed all of those aboard — seven U.S. troops, three members of the Afghan security forces and an Afghan civilian interpreter, said Jamie Graybeal, a spokesman for the coalition.

The U.S.-led NATO force in Afghanistan has relied heavily on utility helicopters such as the Black Hawk to ferry troops, dignitaries and supplies around the mountainous terrain, thus avoiding the threat of ambushes and roadside bombs.

Taliban spokesman Qari Yousef Ahmadi said insurgent fighters shot down the helicopter in Kandahar province on Thursday morning.

"Nobody survived this," Ahmadi told The Associated Press by phone.

Today’s crash is the deadliest since a Turkish helicopter crashed into a house near the Afghan capital, Kabul, on March 16, killing 12 Turkish soldiers on board and four Afghan civilians on the ground, officials said.

In August last year, insurgents shot down a Chinook helicopter, killing 30 American troops, mostly elite Navy SEALs, in Afghanistan’s central Wardak province.

At least 26 Americans have been killed in Afghanistan so far this month and at least 219 so far this year.

Star-Advertiser writer William Cole and The Associated Press contributed to this report.