Train wreck driver's body found
Union: Fear of punishment may have clouded judgment
The search for clues in Japan's train tragedy.
The driver of Monday's train crash in Japan has not been found.
Timeline: Japan rail disasters
World's worst recent train accidents
TOKYO, Japan (CNN) -- More bodies, including that of the train driver, have been found in the twisted wreckage of Japan's deadliest rail disaster in 40 years.
The uniformed body of 23-year-old driver Ryujiro Takami was among those pulled from the scene, officials said Thursday, as the death toll stood at 106.
The number of injured from Monday morning's disaster -- in which a commuter train derailed and crashed into an apartment building near Osaka in western Japan -- remained at 458.
Rescue workers on Thursday called off the search for bodies inside the train's wreckage, but will continue to scour the surrounding area for victims, The Associated Press reported.
One issue in the crash was the inexperience of the driver, on the job for 11 months. The conductor, a 15-year veteran, has been questioned by police.
Police have said they were treating the crash as a case of "possible criminal negligence."
The government on Thursday said it was considering a new train driver certification system in the wake of the disaster, AP reported.
"I wonder if we should be leaving driver qualification to train operators," Transportation Minister Kazuo Kitagawa told reporters Thursday.
"Perhaps the government needs to be more actively involved in driver qualification and training."
Currently, aircraft pilots and ship captains must pass state exams to operate commercial flights and vessels, but there is no state exam to officially certify train drivers, according to Transport Ministry official Yoshihito Maesato.
The driver in Monday's wreck was running 90 seconds late, and railway union leaders said Thursday that fear of severe punishment might have clouded his judgment, AP reported.
Osamu Yomono, vice president of the Japan Federation of Railway Workers, said superiors surround and berate drivers and force them to write "meaningless reports" as punishment.
He said Monday's driver had experienced such treatment for 13 days for a previous error.
"The driver in this accident probably was thinking that he would be subjected to this treatment," AP quoted him as saying. "Fear prevented him from making a rational decision."
Japan Rail West representatives said they were not sure how fast the train was going when it derailed, but noted it would have to be traveling more than 83 mph (133 km/h) to jump the track due to excess speed.
The speed limit along that stretch of track is 43 mph (70 km/h), but survivors allege the train was traveling much faster.
Survivors, in broadcast interviews, said that the train was speeding as it rounded a curve.
The survivors told Japan's national broadcaster NHK that the driver had overrun the previous station and had to back up the train. They said they believe he was trying to make up time.
Analysts said the cause of the crash is likely to be a combination of factors -- including a possible obstruction on the tracks.
"We hear there was a stone on the rail. We hear the train was speeding. There is also speculation that the construction of the train itself may have been faulty. There could be many reasons," one analyst has told CNN.
The Japan Rail West tracks in the area are among the oldest in Japan and do not have an automatic braking system that slows speeding trains. That feature is present on newer tracks.
Meanwhile, two other incidents have further marred the country's normally trouble-free rail system.
A minivan collided with a commuter train in Yokohama early Wednesday, seriously injuring the driver of the vehicle, police said.
No injuries were reported among the 130 passengers on board the train.
The van crashed into the side of the train, operated by Sagami Railway Company, at a crossing at about 9 a.m. (midnight GMT).
On Tuesday a truck driver was injured when a train ran into his semitrailer that had stalled at a crossing north of Tokyo.
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