A train filled with tourists on a weekend outing overturned while descending a mountain Saturday in central Taiwan, killing 17 people and injuring 102, officials said.

A helicopter crash-landed while trying to airlift the victims to hospitals, but there were no serious injuries, authorities said.

The four-car train, with about 150 passengers, was descending Ali Mountain when it slid off the tracks just after the locomotive crossed a small bridge — one of dozens on the steep line.

One of the red-and-green cars tumbled off the bridge into a ravine, while two others were left perpendicular to the tracks. The last car tilted at a 45-degree angle alongside the track.

The cause of the accident was not known. The chief prosecutor for the county of Chiayi, Luo Jian-hsun, said in a television interview that the train crew told investigators the brakes malfunctioned.

Passengers said the train raced down the heavily wooded mountain like a roller coaster.

"The cars suddenly left the rails and fell over," one female passenger — her face and hands streaked with blood — told FTV cable news from a hospital bed.

"The car was filled with people. Some were standing," said the woman. "I looked at my daughter and saw her internal organs. I don't know where my daughter is now."

Li Chien-chuan, vice chairman of the Agricultural Council, said the 10 people aboard the Alouette B234 helicopter were not seriously injured. TV reports showed the damaged aircraft leaning on its side in a thicket. Its rotors were lying in the brush.

The cause of the helicopter crash was not immediately known, officials said.

Officials with the Agricultural Council, which manages the railway, told reporters that the train, which can carry 200 passengers, wasn't overloaded. They also said the train passed its daily safety inspection before going up the mountain Saturday morning.

TV reports showed rescue workers struggling to carry stretchers up the mountain slopes and through thick vegetation. Other footage showed emergency room staffers frantically caring for the injured at a hospital, where relatives wept and wailed over corpses.

Ali Mountain is one of Taiwan's most popular tourist destinations. The Japanese built the narrow-gauge railway when they ruled the island from 1895 to 1945. The rail line, which opened in 1912, was designed to haul lumber from the mountains, but now is mostly used by tourists.

The 44-mile scenic line climbs from the subtropics to pine forests, crossing about 80 bridges and passing through about 50 tunnels.