The death toll from this morning's train crash in Japan has risen to 56, with more than 400 people injured.
Police investigating the cause of the crash say while they have not ruled out speed, they are also looking at the possibility that a stone on the tracks may have derailed the commuter train which was carrying 580 passengers.
Emergency workers are now struggling through the night to rescue four people thought be still alive but trapped in the wreckage and twisted metal.
The crash took place in Amagasaki, near Osaka in western Japan at 9.20am local time (1.20am Irish time).
Survivors of the crash had earlier speculated that the driver may have been trying to make up time because the train was running late.
They said the train appeared to be going too fast and started shaking.
Four carriages were derailed in the collision, with one carriage smashed into the side of an apartment building and another wedged beside it.
Railway officials earlier said the train had overshot the stop line at the previous station before it crashed.
It was Japan's worst accident since November 1963 when 161 people died in Yokohama when a freight train collided with a truck and was then hit by two passenger trains from opposite directions.
In 1991, 42 people were killed and more than 600 injured in a crash in Shigaraki, also in western Japan.
