LISSA, Nigeria — Nigeria said Monday it had requested help from the United States to determine what caused an airliner to slam into the ground, killing all 117 people aboard and carving a pit deep into the earth.

Aviation Minister Babalola Borishad did not rule out foul play as the reason why the Bellview Airlines Boeing 737-200 went down late Saturday north of Lagos, but said: "For now, we just believe it's an accident."

Earlier, the National Civil Aviation Authority chief said a "natural cause" was likely.

"The weather was not too bad but there was lightning, and an airplane struck by lightning could lose total control," Fidelis Onyenyiri said. "There were signs of disintegration which could be caused by impact or other means. Our preliminary position is that the airplane seems to have lost control and went down."

Lightning has rarely been confirmed as the cause of a crash.

MUZAFFARABAD, Pakistan — Trucks carrying more than 100 American soldiers and the U.S. Army's only remaining MASH unit trundled into this quake-ravaged city Monday on a mission Washington hopes will help generate goodwill among Pakistanis.The Oct. 8 earthquake killed an estimated 79,000 people. Many of the injured have yet to receive proper medical care.The 212th Mobile Army Surgical Hospital could save lives, but its arrival was delayed by a shortage of aircraft, vehicle breakdowns and the winding roads of the lower Himalayas.When the unit finally rolled into Muzaffarabad after a 27-hour drive from a military base near Islamabad, it still lacked equipment for major surgeries. That gear had to be returned to the military base because it was on long trailers that could not negotiate the curving mountain roads.