Japanese authorities are still uncertain about the causes of a train derailment in western Japan in which at least 89 people died.
Rescuers were overwhelmed by the number of dead and injured
They are hoping the 23-year-old driver, who may have survived, will be able to shed some light on the accident.
Witnesses have been describing their ordeal on board the train.
"There are a lot of seriously injured people, some with fractures," one passenger, Tatsuya Akashi told public television NHK soon after the accident.
"I've got a lot of blood on my clothes. I don't know what happened," he said.
"It felt like the train speeded up as it was going around a curve and I thought there were some strange swings, and then the train derailed.
"No one knew what happened and everyone kept screaming."
Mr Akashi, who was in the third or fourth carriage, said he was thrown to the floor, several metres away from where he was sitting.
"I landed on top of a pile of other people," he said. "I didn't know what happened, and there were many people bleeding.
"Passengers, many of them high school students, were panicking."
Another survivor, Tsuneo Hara, told AFP news agency: "Passengers who were standing were thrown away and passengers who were sitting were slammed onto the floor. It was just chaos."
Naoto Shimizu, who lives close to the scene, told NHK he heard a loud bang and thought it might have been an explosion at a nearby factory.
"I looked out from my window. I saw nothing unusual near the factory," he said.
"Then I saw dust spreading from the north side, which was large enough to block my view.
"So I thought it must have been a huge accident."
Several witnesses said they thought the train was travelling faster than usual.
A young woman told NHK there had been an announcement apologising for the delay.
"The train was going faster than usual," she added.
"I could not believe what happened to the first three cars. I was glad to be in the fourth carriage."