WASHINGTON (AP) _ A military plane providing support for President Clinton slammed into a steep mountainside just after taking off late Saturday from Jackson, Wyo., where the president had been vacationing.

One Secret Service employee and at least six crew members were aboard the plane, which burst into a fireball in rocky, remote terrain in the Grand Teton range, officials said. Rescue teams on foot and horseback were expected to reach the site _ where smoke and fire lingered for hours _ by daybreak.

``There appears to be some deaths,'' a government official said, speaking on condition of anonymity.

Clinton, who had left the area by helicopter more than five hours earlier, returned safely to the White House Sunday morning after a nine-day vacation during the Republican National Convention. He was notified of the crash early this morning by deputy chief of staff Evelyn Lieberman.

A Clinton administration official said the pilot reported mechanical difficulties and had started to return to the airport. But others cautioned against speculating on why the plane went down.

Arnette Heintz, spokesman for the Secret Service, said six crew members and one Secret Service agent were aboard. He said the employee is a ``physical securities technician,'' who was part of the broad presidential protective team. Heintz said foul play was not considered a factor.

A statement from Dyess Air Force Base, in Abilene, Texas, where the plane was based, said the plane carried ``eight, possibly more'' crew members.

The plane was equipped with both voice and data recorders, said Master Sgt. Sandra Pishner at Dyess Air Force Base.

The crash occurred at 10:28 p.m. MDT at Sleeping Indian Mountain, a popular landmark known for a craggy rock peak shaped like an Indian chief laying on his back. It is located 12 to 15 miles outside of the Jackson airport amid the Grand Tetons range, northwest of Jackson Hole.

``To me it looked like a fire brewing on Sleeping Indian,'' said Tim Tomkinson, night manager of Buskboard Cab Co. ``I saw this guy (at the airport) who said he watched this plane take off heading south, and go left and then it blew up into a ball of flame.''

Witnesses said fires lingered well after a mushroom-shaped fireball sent the starlit sky aglow.

The C-130 was a so-called ``car plane'' that is used to shuttle presidential vehicles. One of the government officials said the cargo included a Secret Service vehicle used in presidential protection, but it was not believed to be a presidential limousine.

Lightning had raced across the sky some five hours earlier, when Clinton left Jackson Hole by helicopter.

Jeff Brown, president of Jackson Hole Aviation said, ``There's no weather associated right now at all. Nobody knows anything at this point except there was a lot of fire.''

The top of the ridge where the plane hit is more than 11,200 feet above sea level, east-southeast of the small airport, according to Brown.

Dan Halloway, operations manager at Jackson Hole Aviation, fueled the plane and said the explosion happened about four or five minutes after takeoff. He said they were loaded up with about 35,000 pounds of fuel.

Ray Coleman of the Teton County Sheriff's Department search and rescue team said helicopters are flying over the site, but the terrain is too rough for anybody to land. Horses will head for the crash site at daybreak, he said.

Fifteen to 20 men were hiking to the site, and would take several hours to get there, he said.

Gini Bright, duty officer for the FAA's northwest mountain regional office in Seattle, Wash., said there were seven people on board the plane.

She said the plane was assigned to the Air Force's 39th Airlift Squadron based out of Dyess AFB and was en route to John F. Kennedy Airport in New York City. Clinton was traveling to New York on Sunday.

The C-130 is turboprop military cargo-troop transport. Designed to be flown by a crew of four, it has a wingspan of 132.6 feet and is 97.8 feet long.

``Whether they flew into the mountain or lost control for some aircraft reason, we don't know,'' Brown said. ``It could have been an inflight shift of cargo or who knows, engine failure, the whole gambit.''

Brown also said officials did not whether the plane was off course. He said nobody had them on the radar, and that they pick planes up on the radar at 13,000 feet.

``No one I know of received any distress calls,'' he said.

``This territory around here is treacherous. You've got to follow the instrument procedures by the letter or you'll get in trouble.''