Taiwanese investigators say the truck blamed for causing a fatal train derailment was already on the tracks when an express train slammed into the vehicle.
The train derailed in a tunnel in Hualien County on Friday, killing 50 people and injuring more than 200. The number of fatalities has been revised downward from 51.
Local media are reporting that the Taiwanese Transportation Safety Board analyzed footage taken by the train's on-board camera and found that the truck had already slid down a sloping road near the tunnel.
The driver, who is among the dead, had apparently applied the train's emergency brakes but could not avoid the collision.
The truck was being used for construction work to make the slope safer. Investigators suspect that the parking brake may have been broken or was not properly engaged.
The driver of the truck was summoned to a court on Sunday. When he left home accompanied by police officers, he said he regrets causing the accident and expressed deep apologies.
He also said he will cooperate with the investigation and never try to evade the responsibility he has to shoulder.
Authorities initially said that it would take about a week before services can fully resume on the line.
But they now say the full resumption will be delayed until April 20 at the earliest, because they need to check the tunnel after the wreckage is removed.