Prosecutors in Taiwan said they have questioned the owner of an unmanned truck that rolled onto a rail track on Friday and caused the country’s worst train disaster in decades.

The train was carrying 494 people at the start of a long holiday weekend when it smashed into a construction truck that slid down a hillside above the tracks, the Taiwan Railway Administration said.

Fifty-one people died in the incident while 146 were injured.

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.

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

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 on Saturday to examine the bodies, office spokeswoman Chou Fang-yi said.

President Tsai Ing-wen was due to visit the site later on 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,” Ms Tsai told reporters on Friday.

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

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

Repair work has also begun 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.

The National Fire Service confirmed the death toll — which included the train’s young, newly married driver and the assistant driver.

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.