Dozens of people have been killed in a train derailment on the east coast of Taiwan, the island’s worst rail disaster in decades.

The 408 Taroko Express was travelling south on the first day of a long weekend, carrying hundreds of passengers towards Taitung, when it crashed inside a tunnel just outside Hualien City at about 9.30am local time, authorities said.

Dozens of people were trapped for hours as rescuers sought to access the “deformed” carriages stuck inside the tunnel.

By mid-afternoon on Friday, at least 51 people, including the train’s 33-year-old driver and a six-year-old girl, were reported by the transport ministry to have died. More than 150 were taken to hospitals with injuries, two of whom later died, and 15 were discharged after examination. Of the dead, 40 people are yet to be identified. The train driver was a recently married young man from Taipei, Taiwan’s United Daily News (UDN) reported.

One passenger told the official news agency CNA that he heard a loud noise and then fell unconscious. When he woke, it was dark and people were using their phones to light the carriage. “I could not bear to look. Many people were lying down,” he said.

The cause of the crash is under investigation, but police said early indications suggested a maintenance vehicle parked incorrectly on a road above the tracks slipped down an embankment, hitting the back carriages of the train. Most of the fatalities were in the rear two carriages, authorities said.