UPDATE 1-Speed control on Taiwan train "malfunctioned" before deadly accident

The train came off the rails on a curve while moving at close to 87 miles per hour (140 kmh), above the speed limit of 46 mph (74 kmh), Wu said.

A speed control system was not functioning when a train in Taiwan crashed killing 18 people and injuring 187, in the island's worst rail disaster in decades, a top investigator said on Tuesday.

It was not clear whether the system, called automatic train protection, had switched off by itself or had been manually disabled before the accident on Sunday, the head of a government-led investigation team, Wu Ze-cheng, told Reuters.

"If the train was above the speed limit, the system should automatically slow it down. It seems like the system had failed. Why? We need more investigation," Wu said.

The train came off the rails on a curve while moving at close to 87 miles per hour (140 kmh), above the speed limit of 46 mph (74 kmh), Wu said.

More investigation was needed to determine the cause, he added.

The driver of the train, You Zhen-zhong, 48, was granted bail of T$500,000 ($16,167) on Tuesday after being detained for investigation, the Taiwan Railways Administration said.

You had been treated in hospital following the accident in Yilan County, in the island's mountainous northeast.

The train data recorder, which tracks speed, among other things, had been sent to prosecutors to be examined.

The disaster was Taiwan's deadliest rail accident since a 1981 collision that killed 30 people.

The head of the state railway administration, Lu Jie-Shen, had offered to resign but that was not accepted by the transport minister, the railway authority said.

Premier William Lai apologised for the accident on behalf of the government.

"People expected the railway to be the safest," Lai told parliament.

"I apologize to the people on behalf of the Executive Yuan," he said, referring to the island's cabinet.

Train derailments are not uncommon on the island, which has rough, mountainous terrain, but deadly accidents are rare.