Rescue workers continue to search for at least three people trapped in the wreckage of a commuter train that derailed and smashed into an apartment building in western Japan Monday, killing at least 57.

Around 440 people were reported injured in Japan's worst rail accident in 42 years.

Police said the train was travelling at nearly twice the speed limit for the section of track it was using when the crash occurred at about 9:20 a.m. local time Monday.

Rescuers gather around the wreckage of a derailed commuter train. (AP Photo)

The disaster happened near the city of Osaka, about 400 kilometres west of Tokyo.

Investigators were trying to determine if the excessive speed of the train or the actions of the 23-year-old driver, who has been on the job for 11 months, caused the crash.

The fate of the driver was unknown.

A passenger is rescued from a train in western Japan on Monday after a seven-car commuter train derailed. (AP Photo/Kyodo News)

The seven-car train, which was carrying 580 passengers, had plowed into a car at a crossing before careening into the apartment building.

The crash was initially attributed to that collision, but authorities later backtracked and said the driver may have been speeding.

West Japan Railway Co. said its initial investigation found that the derailment happened about 100 metres before the crossing where the car was hit.

At one point, railway officials were saying that someone pulled the emergency brake as the train sped into a curve, causing the derailment.

Crash survivors had been using their cellular phones to call for help from within the wreckage.

Tsunemi Murakami, safety director for train operator West Japan Railway Co., estimated that the train would have had to be going 132 km/h to have jumped the track because of excessive speed.

The crash happened at a curve that required the driver to slow to 69 km/h.

Murakami said it still was not certain how fast the train was going. But a crew member and survivors reported that the train, which was reportedly two minutes behind schedule, was travelling faster than usual.

Company president Takeshi Kakiuchi expressed sorrow at the accident, but said rescuing survivors would take priority Monday over determining a cause of the crash.

Train accidents are rare in Japan, where high-speed railways are one of the main forms of intercity transport.

Monday's crash was the deadliest in Japan since a 1963 wreck in suburban Tokyo killed 161 people.

The most serious recent accident before Monday's derailment came in 1991, when a crash killed 42 people in Shigaraki, western Japan.

With a report from Agence France-Presse