Japanese officials have begun looking for clues as to how a packed commuter train derailed, causing the country's worst rail tragedy in 42 years.
Every inch of the track is being carefully examined
At least 73 died and 450 were injured, but as rescuers worked throughout the night three people were pulled alive from the wreckage early on Tuesday.
The commuter train slammed into an apartment block near Osaka on Monday.
Officials said they would examine a range of possible explanations for the crash, including driver error.
A second passenger train derailed on Tuesday after hitting a truck at a crossing in Ibaraki prefecture, north of Tokyo.
The driver of the truck was slightly hurt but there were no immediate reports of any other injuries, the Associated Press news agency said.
There were 580 passengers on board the crowded train when it derailed at 0920 (0020 GMT), towards the end of the rush hour.
The train's front two carriages were smashed and flattened against the nine-storey apartment block by the force of the impact.
Rescuers at the scene in Amagasaki, 410km (255 miles) west of Tokyo, worked through the night to free remaining survivors.
The three pulled from the train early on Tuesday have all been transferred to hospital for treatment.
A number of bodies are believed to still be trapped inside the wreckage.
The bodies of those killed were taken to a makeshift morgue set up in a local gymnasium where throughout the day and night relatives arrived to identify their loved ones.
"I thought he would be alive in a hospital somewhere," one woman who lost her son told TV channel NHK. "I only saw him last night and I never dreamed I would be parted from him today."
Initial suspicions on the cause of the crash focussed on the role of the train's 23-year-old driver.
Ryujiro Takami, who remains unaccounted for, had just 11 months experience and was reprimanded in 2004 for overrunning a station.
Passengers and rail officials said the train overshot a station platform shortly before it derailed at 0920 (0020 GMT) on Monday.
Japanese government and transport company officials promised a full investigation into the disaster.
Transport Minister Kazuo Kitagawa, who visited the scene, described the crash as a "horrible and serious disaster".
JAPAN'S RAIL SAFETY RECORD
1963: Freight train crashes into derailed commuter train in Tokyo, 161 people killed
April 1991 - 42 killed when two trains collide near Shigaraki
March 2000 - Tokyo subway train crashes into derailed train, killing five
April 2005 - Crash near Osaka kills at least 50
Japan's Prime Minister Junichiro Koizumi said the shock of the accident must prompt a renewed focus on safety standards.
Passengers told of their panic as the speeding train began to leave the track.
"The train overran a stop at the previous station and so it backtracked, so I guess the driver was in a hurry because the train was running late," one survivor told Japanese television.
"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," passenger Tatsuya Akashi told NHK television.
"No one knew what happened and everyone kept screaming."
Another passenger, 64-year-old housewife Etsuko Murakami, described the impact as "the most fearful moment of my life".
The force of the impact threw five of the seven cars off the rails.
Rail experts suggested that the train would have to have been travelling at about twice the 70kph (43mph) speed limit to flip off the track.
Japan's railway system, used by nearly 60 million people every day, is widely considered to be one of the world's safest.
This is the worst rail accident in Japan since a three-train crash killed 161 near Tokyo in 1963.
JAPAN RAIL CRASH
1: Crash happened at 0020GMT at end of morning rush-hour
2: Seven-carriage train had 580 people aboard
3: Four of the carriages derailed (one not visible)