A bridge girder fell to the ground at a construction site for the Seishin bypass in Shizuoka city. (Yuichi Koyama)

SHIZUOKA--The land ministry is investigating what caused the deadly accident here involving a falling bridge girder, but one general contractor has said an “unbelievable mistake” was committed.

The 63-meter-long girder weighing 140 tons fell about 9 meters to the ground early on July 6 during work on the elevated Seishin bypass in Shizuoka city. Two workers were killed and six were injured.

Workers had jacked up the girder near the center of the bridge piers and were sliding it to the bearing point near the edge of the piers.

The girder then fell, with workers still on top of it.

“People sometimes stand on the girder to prepare for moving it and check if it’s sliding properly,” said Osaka-based Namura Shipbuilding Co., which is involved in the expressway construction work.

The ministry’s Shizuoka National Route office and Namura Shipbuilding explained the procedure for installing such bridge girders.

The first step is to assemble the girder near the site. The girder is then moved onto the bridge piers, and finally fixed to the piers.

The accident occurred just before the final step.

According to a contractor involved in bridge construction in the Tokai region, this procedure can be time-consuming and expensive, but it can be used even in a narrow site.

“It is dangerous to have people on the bridge girder while moving it, so we basically do not do so,” the contractor said.

A senior official of a major general contractor said the falling girder was an “unbelievable mistake.”

“The method is not unusual and not particularly difficult,” the official said. “I don’t know exactly what happened at that site, but I can’t believe it.”

The ministry said on July 6 that it would set up an accident investigation committee to determine the cause and prevent a recurrence.

(This article was written by Arata Mitsui, Daisuke Yajima and Noboru Inoue.)