A CH-53D Sea Stallion helicopter from Marine Corps Base Hawaii at Kaneohe Bay crashed in southern Afghanistan Thursday, officials confirmed.

Six International Security Assistance Force service members died after the crash in southern Afghanistan, ISAF said in a news release.

Fox News reported the dead are U.S. Marines. No identifications have been released.

ISAF said the cause of the crash is under investigation, but initial reporting indicates there was no enemy activity in the area at the time of the crash.

The release did not say how many were on the helicopter or whether any others were injured.

All the Marine Corps’ Vietnam War-era Sea Stallion helicopters are based at Kaneohe Bay. Marine Heavy Helicopter Squadron 363 out of Hawaii deployed to Afghanistan in August, replacing another Hawaii unit, Marine Heavy Helicopter Squadron 463.

Marine Corps Base Hawaii referred questions to U.S. Central Command in Florida, which has command responsibility for Afghanistan. Officials there were not immediately able to provide more information.

The Sea Stallion squadron now in Afghanistan was the same unit that lost a crew member in the crash of one of the helicopters March 29 in Kaneohe Bay.

Cpl. Jonathan D. Faircloth, 22, who had survived combat tours in Afghanistan and Iraq, was killed, and three other crew members were injured, after the 88-foot-long helicopter made a "hard impact" landing from an altitude of about 300 feet while on a night training flight, the Marine Corps said.

According to a Field Flight Performance Board investigation conducted by the Marines and obtained by the Star-Advertiser through the Freedom of Information Act, the chopper crashed as a result of a "catastrophic mechanical failure."

The crew’s reaction to the mechanical failure was consistent with training procedures and not faulted. Despite repeated requests, the Corps still has not released further investigation results, including the cause of the mechanical failure.

The twin-engined CH-53D first flew in 1964 and became operational in 1966, according to the Navy. In the mid-1990s the Marine Corps consolidated all its remaining Sea Stallions at Kaneohe.

It is now used as a medium-lift helicopter. The Marines in Hawaii have started to swap out some of the older two-engine CH-53Ds with the newer CH-53E Super Stallion, a more powerful, three-engine variant that fulfills a heavy-lift role.

At least five of an anticipated squadron complement of 12 Super Stallions are in Hawaii. Other older Sea Stallions are expected to be replaced in Hawaii by MV-22 Osprey tilt-rotor aircraft.

The Marine Corps said in May that all of the CH-53Ds in three squadrons at Kaneohe Bay were expected to be retired from service in the next year and a half.

A squadron of 12 MV-22 tilt-rotor Osprey aircraft is tentatively scheduled to arrive in Hawaii in 2014, the Corps said.

Most of the remaining Sea Stallions based at Kaneohe Bay are about 40 years old, base officials said.

In 2006 Sea Stallion squadrons at Kaneohe Bay started to deploy to Iraq, and now regularly deploy to Afghanistan.

The Marine Corps previously said that as a cost-saving move, 11 Sea Stallions stayed in Afghanistan, and deploying crews fell in on those same helicopters instead of transporting aircraft back and forth from Hawaii.

The Sea Stallions have received periodic upgrades, but maintenance crews as far back as 2003 were making several trips a year to a helicopter "bone yard" outside Tucson, Ariz., to retrieve parts such as engine cowlings that were not made anymore.

A "sundown" ceremony had been scheduled in Hawaii next month to recognize the long service of the Sea Stallions, and one of the choppers was expected to be flown to the Pacific Aviation Museum Pearl Harbor to become a museum piece.

The Marines at Kaneohe Bay in 2005 paid a steep price in life in the crash of a CH-53 Super Stallion — the three-engine variant now in widespread use in the Corps — that went down in a sandstorm in western Iraq.

The crew of the California-based helicopter became disoriented on Jan. 26, 2005, when weather turned bad and mistakenly flew the transport chopper into the ground, investigators determined.

Of 31 killed, 26 Marines and a sailor were from Kaneohe Bay.