KAPRUN, Austria (AP) _ A cable car crammed to capacity with skiers and snowboarders caught fire Saturday while being pulled through an Alpine tunnel, trapping the passengers deep inside a mountain and killing about 170 people _ many of them children and teen-agers.

Most of the victims apparently managed to escape the burning car but were killed by acrid smoke as they tried to flee by running upward on narrow stairs leading out of the tunnel, said Manfred Mueller, the head of cable car technical operations. The few survivors among the 180 people on board apparently ran the opposite way, evading most of the smoke being blown upward by strong drafts pushing through the tunnel.

“Most of them were youths,” Salzburg Gov. Franz Schausberger said of the dead in an interview with state television. “Today is a day of mourning.”

Rescuers were unable to reach the car as the fire raged for hours, sending smoke spewing from the mouth of the tunnel below. The blaze burned the car down to the chassis, firefighters said. Authorities said they still didn’t know what caused the fire.

An area hospital said 19 Germans and Austrians were brought in by ambulance _ apparently nine who escaped from the car and 10 who were waiting just inside the tunnel entrance to board the next car up, hospital officials said. All suffered cuts, bruises and the effects of smoke inhalation. One was in serious condition with injuries to the lungs suffered from breathing in noxious fumes. Three had left hospital by evening.

One survivor described “horrible scenes” as passengers desperately tried to find a way out of the smoke-filled cabin.

“They tried to rip open the shut doors and to break windows,” the survivor told the Austria Press Agency, which did not give a name. “My only thought was to get out, and I was able to save myself in the last second because a window was kicked in and I could fight my way outside.”

As night fell, relatives and friends of unaccounted-for skiers gathered in the nearby Alpine village of Kaprun, waiting and hoping that their loved ones were not among those killed in the smoky tunnel. One man from the neighboring town of Mittersill was waiting, hoping his son Marcus, 16, would be among the survivors.

“My son went up there with one of his friends,” said the man, who asked not to be identified. “A friend works at the cable car. He gave him two free passes.”

Nearby, a woman and her daughter clasped each other, crying wordlessly. At one end of the hall, volunteers entered name after name into computers, recording people who were still alive and had been tracked down in nearby hotels.

By around midnight, about 2,500 people who had been on the glacier slope at the time of the tragedy had been located. Among those still missing were six Americans, part of a ski club from the U.S. military’s Leighton Barracks in Wuerzburg, Germany, said Maj. Drew Stathis, one of the group. It was unclear whether the Americans had been aboard the car.

“Our group is praying for six of them,” said Stathis. He said among the missing was a family of four, including two children.

The tragedy appeared to be the most serious ever involving cable-driven ski transportation. In 1976, 42 people died after a cable snapped at the Italian ski resort of Cavalese.

The passengers were riding the cable car more than 3,200 yards up Kitzsteinhorn mountain to enjoy late fall sunshine and balmy weather at the popular glacial peak and ski resort. But as the car was pulled through the long tunnel that burrows into the mountain, fire broke out, leaving it trapped 600 yards inside the tunnel.

Reporters near the scene were told that fresh air sucked into the tunnel fed the flames, which apparently broke out in the front compartment occupied by a cable car attendant. The blaze “spread at a raging speed _ like a fireplace,” Schausberger said.

Among the dead were three people waiting in a passenger area at the tunnel’s uphill end, he said. They died of smoke inhalation. Also killed was the cable car attendant in an otherwise empty car that was going toward the valley as the one carrying the other victims was going up.

Running on rails, the cable car enters the mountainside after being hoisted up a steep ramp over a valley, supported by metal struts.

Mueller, the head of technical operations, said an alarm sounded and the cable car attendant was told to open the doors. Minutes later, officials lost radio contact with the attendant. It was unclear whether the doors ever opened.

Schausberger said he was at a loss to explain what happened. “Everything was fine” when inspectors from the transport ministry checked the cable car system in September, he told reporters.

A massive rescue operation was mounted with some 13 helicopters, teams of police, doctors and Red Cross workers all at the site. Helicopters also made their way from neighboring Bavaria, in southern Germany, carrying firefighters with special equipment. The Red Cross assembled a team of 40 psychologists to help relatives cope with their grief.

Late in the evening, about 100 local residents, firefighters and rescue crews still in their oilskins gathered at the local fire hall for a memorial service for the dead. Three of the bodies _ apparently those who died in the passenger waiting area _ were placed in closed caskets in the hall.

The Kitzsteinhorn resort, about 60 miles south of Salzburg in the heart of the Austrian Alps, is a popular summer and early winter skiing area with Europeans and vacationing Americans alike.

The cable car system, also called a funicular train, was built in 1974 and modernized six years ago to include two state-of-the-art cars and technology. It can transport some 1,500 people from the valley station to the summit each hour. The system has never before recorded an accident, said Hans Wallner, the director of the tourist region of Kaprun.

Experts said the cable car system was supposed to be fireproof.

Austria’s president, Thomas Klestil, expressed condolences to relatives, and the government declared Saturday and Sunday national days of mourning. Schausberger also declared Saturday a day of mourning in Salzburg province.

–MELISSA EDDY