A forest fire burning out of control in the Grand Teton National Park forced National Park Service officials tonight to close a major highway, tow cars parked at trailheads and consider evacuating the park's most popular campground.

Some hikers and climbers were temporarily stranded in the Teton mountains as the windswept fire approached or crossed the bottoms of the trails they were using.

At least one elderly person was still high up on a heavily used trail leading to two alpine lakes on the east flank of Grand Teton.

The fire, which started south of Taggart Lake, swept northward along the east flank of the spectacular mountain range. At mid-afternoon it leaped ahead about half a mile to cross Bradley Lake. North of there hikers hurried down the Glacier and Garnet Canyon trails just ahead of the fire.

Park ranger Peter Armington, who is in charge of fighting the fire, said all the trails were closed.

No evacuation of the hikers was attempted. "We hope they have sense enough not to walk down into the fire," Armington said.

A huge pall of smoke hung over the Jackson Hole valley at sundown. Park visitors coming from the south were being turned back at the Moose Village entrance.

Earlier, hundreds of cars lined the road as their occupants took pictures of the fire approaching within a few hundred feet.

The Highlands, an area of about 15 vacation homes, was evacuated. Several buildings at historic Climbers Ranch, a hostelry operated by the American Alpine Club for mountain climbers, were burning. Some cars left there by climbers appeared likely to become engulfed in the flames.

Ed Christian, assistant chief ranger for the park, said the fire probably was caused by a recent lightning strike or a flare-up from a small fire in the area several days ago.

About 40 park service and 15 U.S. Forest Service personnel were fighting the fire late today with others arriving steadily.

A forest service "slurry" plane from Missoula, Mont., and a helicopter with buckets were dropping water on the blaze.

The helicopter also evacuated a firefighter who sustained a serious injury when he cut his knee with a chain saw while working on a fire break.

The fire crews were trying to keep the fire from crossing Teton Park Road, the highway that runs along the hills at the foot of the mountains. Smoke obscured the mountains from many parts of the huge valley above which the mountains loom some 7,000 feet.

The fire moved swiftly because of strong wind and because the area, like many sections of the West, has been unusually dry all summer. Elsewhere today, more than 6,000 firefighters fought blazes that have ravaged nearly 65,000 acres of brush and timberland in Washington, Idaho and Oregon.

The fire here, Christian said, was fed by "excellent fuels . . . spruce bud kills and wind-downed trees."

As the flames worked their way northward toward Lupine Meadows south of Jenny Lake, the park's most popular campground, cars were towed from a major trailhead there.

Officials were worried that the fire would sweep out onto the sagebrush- and grass-covered meadows and into the trees surrounding Jenny Lake. The area includes 49 campsites, a ranger station, a store and the Jenny Lake Lodge and cabins.

Bridger-Teton fire management officer John Chapman said the blaze had burned over 350 acres and was still out of control. There has been no significant rain in the valley for 26 days, he said.

This afternoon, Chapman spoke into his radio, saying, "Order a Class 1 team," meaning that he was calling in a crew of the forest service's most experienced firefighters.

The fire was so intense -- and all the grass, brush and trees so dry -- that officials were afraid to light backfires in an effort to contain it, Chapman added.

As the wind abated at sundown, the fire began to spread toward the south and southeast. In its path was the former park headquarters at Beaver Creek, which is now used as a residential, office and storage complex.

As the fire approached Beaver Creek, power to the complex was shut off.

Teton County school buses were pressed into service to move firefighters there from other previously critical points and park service employes anxiously headed there to try to remove the trailers in which they live.