Two days after Taiwan¡¯s deadliest rail disaster in decades, investigators were working to determine why a truck had slipped downhill from a construction site into the path of an express train, resulting in the collision and derailment that killed dozens of people.

The operator of the crane truck, Lee Yi-hsiang, was ordered detained Sunday by a judge, who reversed an earlier decision to grant him bail. Lee, who has not been charged with a crime, told reporters he had caused the crash and said he would take full responsibility for it.

¡°I hereby express my deep regret and my sincerest apologies,¡± Lee said, his voice choking as he bowed in apology.