Prosecutors in Taiwan said Saturday they questioned the owner of an unmanned truck that rolled onto a rail track and caused the country's worst train disaster in decades that killed 51 people and injured 146, though no charges have been filed.

The train was carrying 494 people at the start of a long holiday weekend on Friday when it smashed into the construction truck that slid down a hillside above the tracks, the Taiwan Railways Administration said. Many passengers were crushed just before the train entered a tunnel, while some survivors were forced to climb out of windows and walk along the train’s roof to safety.

Also read: Also read: Train hits truck that slid onto track in Taiwan, killing 51

The truck’s emergency brake was not properly engaged, according to the government’s disaster relief center.

The district prosecutor's office in eastern Hualien County, where the train derailed, confirmed it had interviewed the truck owner, among others, but was not ready to file charges. Prosecutorial staff were visiting a mortuary Saturday to examine the bodies, office spokeswoman Chou Fang-yi said.

President Tsai Ing-wen was due to visit the site later Saturday.

“We have asked the Transportation Safety Committee to conduct a strict investigation of the accident, and after fully clarifying the cause of the accident, we will explain it to everyone," Tsai told reporters Friday.

“We’re asking passengers to forgive us for any delays,” she said.

Transportation Minister Lin Chia-lung said repairs will be accelerated.

“When such a thing happens, I feel very sorry and I will take full responsibility,” Lin said after touring the site.

Taiwan Railways Administration chief Chi Wen-chung said his team had successfully removed the first derailed carriage out of the site.

Two large construction cranes could be seen drawn up next to the train, as workers examined and removed some parts in a remote wooded cliff area on the island’s east coast.

Repair work also was underway on the tracks including the tunnel where part of the eight-car train crashed. The operation should be done within a week, said Weng Hui-ping, head of the railway administration’s news group. During the repairs, all east coast trains will run on a track parallel to the one damaged in the accident, causing delays of 15 to 20 minutes, he said.

Also read: Train crashes in eastern Taiwan, killing 48, injuring dozens

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 government's disaster response center said it was the worst rail disaster in 73 years.

Train travel is popular during Taiwan’s four-day Tomb Sweeping holiday, when families often return to hometowns to pay respects at the gravesites of their elders.

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.