A train barreled into an unmanned truck that had rolled onto the track Friday in Taiwan, leaving at least 51 people dead and dozens injured in the island’s deadliest rail disaster. Many passengers were crushed, while some survivors were forced to climb out of windows and walk along the train’s roof to safety.

The truck’s emergency brake was not properly engaged, according to the government’s disaster relief center, and the vehicle slid about 20 meters (65 feet) down a hillside. Minutes later, the train’s lead car crashed into it, according to Railways Administration official Weng Hui-ping, just before the train entered a tunnel.

The train, which was carrying more than 400 people, derailed near the Taroko Gorge scenic area on the first day of a long holiday weekend when many people were using Taiwan’s extensive rail system, including many families with children. Images from the scene showed the train’s cars wedged against the tunnel’s walls. Part of the wall of one car had smashed into a seat.

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“Many people were crushed under train seats in the collision. And there were other people on top of the seats. So those at the bottom were pressed and crushed and lost consciousness,” a passenger with gauze taped to her elbow told Taiwanese broadcaster EBC, which did not show her face or give her name. “At the beginning, they still responded when we called them. But I guess they lost consciousness afterward.”

The National Fire Service confirmed the death toll — which included the train’s young, newly married driver and the assistant driver — and said more than 100 people were injured.

The service earlier said all passengers had been accounted for, but a spokesperson later said there may be more bodies trapped in the mangled cars and the death toll may still rise. The spokesperson spoke on condition of anonymity because they were not allowed to release the information to media.

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Weng, of the Railways Administration, called the crash Taiwan’s deadliest rail disaster.

He said a construction truck whose owner was a contractor for the administration slid from a work site above the track. No one was in the truck at the time. An investigation has been launched, and Hualien police have interviewed one person, Weng said.

The stretch of track where the orange-striped train came to a halt hugs the coastline and lacks any protective fencing. Yellow and red police tape marked the area of the crash, where tents had been set up and dozens of rescuers and officials had converged.

With much of the train still inside the tunnel, many escaping passengers had to scramble out of doors and windows and scale the sides of the train to walk along the roof in darkness to safety.

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One young man interviewed by Taiwanese media at a hospital said he had traveled with friends for the holiday but now had no idea where they were.

“Everyone just went flying all over the place,” said the man, who only gave his surname as Chen and who was in a wheelchair, his arm in a cast. Obviously distraught and in pain, he said the cars and seats had been twisted out of shape.

Taiwan is a mountainous island, and most of its 24 million people live in the flatlands along the northern and western coasts that are home to most of the island’s farmland, biggest cities and high-tech industries. The lightly populated east where the crash happened is popular with tourists, many of whom travel there by train to avoid mountain roads.

In a tweet, Taiwanese President Tsai Ing-wen said emergency services “have been fully mobilized to rescue & assist the passengers & railway staff affected. We will continue to do everything we can to ensure their safety in the wake of this heartbreaking incident.”

The crash came on the first day of the four-day Tomb Sweeping Festival, an annual religious holiday when people travel to their hometowns for family gatherings and to pay their respects at the graves of their ancestors.

Taiwanese Premier Su Tseng-chang said the Railways Administration would be required to immediately conduct checks along other track lines to “prevent this from happening again.”

About 50 volunteers from the Tzu Chi Buddhist Foundation stationed at an aid tent near the crash site said children were among the dozens who escaped the train cars. They were treating minor wounds and offering lunches.

“We see people coming off the train and they look shaken and nervous,” said Chen Tzu-chong, a Tzu Chi team leader on site.

Taiwan’s last major rail crash was in October 2018, when an express train derailed while rounding a tight corner on the northeast coast, killing at least 18 people and injuring nearly 200.

In 1991, a collision in western Taiwan killed 30 people and another crash a decade earlier also killed 30. Those were said to be the worst previous crashes on the rail system that dates from the late 19th century.

Taiwan’s extensive rail system has undergone substantial upgrades in recent years, particularly with the addition of a high-speed line connecting the capital Taipei with west coast cities to the south.

The train involved in Friday’s derailment, the Taroko No. 408, sometimes called the Taroko Express, is one of Taiwan’s newer models.