As wreckage was cleared away the front car became visible Enlarge Image

One option being considered is a state supervised test for all train drivers.

The call came as emergency workers ended the rescue operation, after the death toll rose to 106. One of the dead was confirmed as the train's driver.

Rail union leaders said the crash may have been caused by the driver's fear of being reprimanded for running late.

"I wonder if we should be leaving driver qualification to train operators," Transport Minister Kazuo Kitagawa told reporters.

"Perhaps the government needs to be more actively involved in driver qualification and training," he said.

Doubts over driver

Accident investigators said the JR West train's 23-year-old driver, Ryujiro Takami, may have been trying to make up time.

Because of a mistake he had made at a previous station, Takami's train was running 90 seconds late - potentially disruptive on Japan's meticulously scheduled rail network.

In pictures: Crash aftermath Survivors tell of chaos

Stones on the rails have also been suggested as another possible factor in the crash.

The BBC's correspondent in Tokyo, Jonathan Head, says questions are being raised about the obsession with punctuality in Japan.

According to railway employees, they can be subject to severe punishment if their trains run late.

"The accident is a result of JR West's... high-pressure management, which uses terror to force its employees to follow orders," Osamu Yomono, vice-president of the Japan Confederation of Railway Workers' Unions, told reporters.

He said punishment included ordering errant workers to repeatedly write "meaningless" reports or undertake humiliating tasks.

JAPAN'S RAIL SAFETY RECORD 1963: Freight train crashes into derailed Tokyo commuter train, 161 killed April 1991 - 42 killed when two trains collide near Shigaraki March 2000 - Tokyo underground train crashes into derailed train, killing five April 2005 - Crash near Osaka kills at least 89

He had only been in the job for 11 months, but is reported to have been reprimanded twice in his previous job as a conductor, and once last year as a driver for a platform overrun.

Rescuers found Takami's body on Thursday. Shortly after that, the mangled remains of the first carriage were finally dragged out from under the apartment block in the western city of Amagasaki that it struck on Monday.

Rescue workers have been using high-tech sensor equipment to listen for heartbeats or breathing, but no-one has been found alive in the wreckage since early on Tuesday morning when three survivors were discovered and safely removed.

About 450 people were also injured in the incident, which is Japan's worst since a train collision killed 161 people near Tokyo in 1963.

The crash has prompted questions about Japan's railway system, which handles 60 million passenger journeys every day and which has been regarded as one of the world's safest.

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)