An American military helicopter went down Sunday in Afghanistan's rocky mountains after experiencing a mechanical malfunction, leaving two Marines dead and five others moderately injured.

The CH-53E Super Stallion had just departed from a former Soviet base near Kabul on a resupply mission when it crash-landed about 40 miles south of Bagram air base, according to military officials. A second chopper accompanied the doomed aircraft on the mission.

Defense Secretary Donald Rumsfeld said he believed a mechanical failure downed the aircraft.

"It appears to be, at the moment, a mechanical problem with the helicopter," Rumsfeld said on NBC's Meet the Press. "Your heart just breaks every time something like this happens."

Marine spokesman 1st Lt. James Jarvis also said there was no initial indication of hostile fire.

In Washington, the Pentagon identified the dead as Staff Sgt. Walter F. Cohee III, 26, from Mardela Springs, Md., a communications navigations systems technician, and Sgt. Dwight J. Morgan, 24, from Mendocino, Calif., a helicopter mechanic.

It was the third fatal accident involving a military helicopter since the war in Afghanistan began Oct. 7.

The survivors were flown from the crash site to Bagram and on to another, undisclosed site in Afghanistan for treatment, said Capt. Tom Bryant, a U.S. Army spokesman at Bagram. The Pentagon said their injuries were not life-threatening.

The injured were: Cpl. David. J. Lynne, 23, from Mecklenburg, N.C.; Cpl. Ivan A. Montanez, 22, from Hayes, Texas; Cpl. Stephen A. Sullivan, 24, from Pickens, S.C.; Capt. William J. Cody, 30, from Middlesex, N.J., and Capt. Douglas V. Glasgow, 33, from Wayne, Ohio.

The men were assigned to Marine Heavy Helicopter Squadron 361, which is part of the 3rd Marine Aircraft Wing based in Marine Corps Air Station, Miramar, Calif.

"The site was quickly secured," Bryant said. "We quickly got medical personnel and others on the ground, got them evacuated back here. We have a robust medical treatment capability here."

Bryant would not say which U.S. forces were being resupplied. Small units of special forces have been scouring the country for leaders of Usama bin Laden's Al Qaeda terror network — blamed for the Sept. 11 attacks in New York and Washington — and the deposed Taliban regime that supported them.

The crash occurred at about 8 a.m. local time at an altitude of between 7,000 and 9,000 feet. Rescuers were able to land next to the site, speeding up the evacuation of the injured, Jarvis said.

"Our hearts and prayers go out" to the families, he said.

The worst single casualty toll for U.S. forces in the Afghanistan campaign came Jan. 9, when all seven Marines aboard a refueling tanker were killed in a fiery crash near Shamsi air base in remote southwestern Pakistan.

The cause of that crash remains under investigation, though Marines said there was no sign of hostile ground fire.

The only other fatal crash of a U.S. military aircraft during the war occurred Oct. 19, when an Army Black Hawk helicopter crashed in Pakistan, killing two Army Rangers.

An American soldier was killed in an ambush in eastern Afghanistan earlier this month, and a Central Intelligence Agency operative died during an uprising by Al Qaeda and Taliban prisoners in the northern city of Mazar-e-Sharif in November.

The Associated Press contributed to this report.