Police on Tuesday said they suspect malfunctioning brake parts caused Sunday's fatal collision between two Keifuku Electric Railroad Co. trains in Fukui Prefecture.
The crash killed one of the drivers and injured 25 passengers.
Transport Ministry officials say the train's brake rods had snapped, adding that they suspect the parts were already cracked prior to the accident.
Inspectors of the train, which failed to stop at the end of a branch line and continued on to the main line, found that the brakes failed to operate even though the brake lever had been set in the emergency position. This should have brought the train to a rapid halt, police said.