Prosecutors investigating Taiwan’s worst railway disaster in seven decades have appealed to the public for any photographs they may have taken of the crash that killed at least 50 people.

Hualien County prosecutor Yu Hsiu-tuan said people may have inadvertently gathered evidence in their photos, particularly about individuals observing the crash scene from a construction site above.

The disaster on Friday was believed to have been caused when a construction truck parked on a steep slope slid down the hillside onto the tracks in front of the Taroko Express train as it sped towards a tunnel at 81 miles per hour.

The train was carrying 494 people, about 150 of whom had standing tickets, when it slammed into the truck and derailed when entering the tunnel, crushing many passengers inside the carriages.

The truck had been driven by construction site supervisor Lee Yi-hsiang, who was taken into custody on Sunday after having initially been released on bail. Lee, who is believed to have failed to engage the truck’s handbrake, offered a tearful apology while being taken from home, saying he would “co-operate with the authorities’ investigation fully, and take responsibility”.

Lee has a previous conviction for falsifying documents related to construction work and was considered a flight risk.

Investigators have said the driver of the train probably had just 6.9 seconds to react to the truck on the tracks. Both the train driver and the assistant driver were killed and most of the fatalities were in the front four cars of the eight-car train.

The sale of standing room-only tickets and the lack of protective fencing along the tracks, which run along a narrow strip between a steep hillside and the Pacific Ocean, have been cited as possibly contributing factors to the disaster.

Transport minister Lin Chia-lung tendered his resignation on Sunday, saying he would “take ultimate responsibility”. Premier Su Tseng-chang has told him to stay on for the time being and Mr Lin and others are due to report to the legislature on Wednesday about the disaster.

Mr Lin was also minister during Taiwan’s last major rail crash in October 2018, when an express train derailed while rounding a tight corner on the north-east coast at high speed, killing at least 18 people and injuring nearly 200.

Wrecks in 1981 and 1991 also killed 30 and 31 people. Taiwan’s worst rail disaster was in 1948, when a train caught fire in suburban Taipei, killing 64 people.

The most recent disaster struck on the first day of the annual four-day Tomb Sweeping holiday, when families often return to their home towns to pay respects at the gravesites of their elders. It’s also an opportunity to take a holiday and many of the passengers were families with children.

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 as a tourist destination, and the railway line is known for its beautiful natural scenery.