The death toll in Japan's worst rail accident in four decades looked set to rise to more than 100 as hopes faded that more survivors would be found in the wreckage.
The official death toll stood at 91 after rescue crews extracted 18 bodies from a mangled carriage overnight.
But there was little hope for the dozen or so people still trapped inside another carriage, embedded in a ground-floor car park under the building on the outskirts of the city of Osaka.
"Unfortunately, time has passed but we're carrying on and have not given up," said a fire department official.
Rescue teams were using equipment to detect heart beats with electromagnetic waves.
Police raided the offices of the train's operator yesterday looking for clues to the cause of the crash, which investigators said could have been linked to excessive speed after the train's driver fell more than a minute behind schedule.
The government, keen to avoid any erosion of confidence in a rail system that transports more than 21 billion people a year, pledged to ensure the safety of the country's railways.
"The government as one, will do its utmost to find out the cause of the accident and prevent a reoccurrence," Transport Minister Kazuo Kitagawa told parliament.
Even as he spoke, news emerged that a commuter train in Yokohama, near Tokyo, had collided with a van at a crossing. None of the train's passengers was hurt, but the van's driver was taken to hospital in serious condition.
Investigations into Monday's crash were focusing on speed as well as other factors such as rail design that might have caused the packed train to jump the tracks as it rounded a curve.
Data recorded in the train's system showed it was traveling at 62 miles an hour as it approached the site of the accident, where the speed limit was 43 mph. But analysts said speed alone would not likely have led to the disaster.