A bridge girder slipped off a raised platform at a construction site in central Japan early Thursday, leaving two workers dead and six others injured, police said.

Four of the six were seriously hurt and two sustained minor injuries in the incident in Shizuoka Prefecture at around 3:10 a.m., but none are in a life-threatening condition, the police said.

Around 30 construction workers were building a multi-level bypass when the accident took place. The two killed were in their 50s.

The site at an elevated bypass under construction in Shizuoka where a bridge girder fell from a height of some 9 meters is pictured from a Kyodo News helicopter on July 6, 2023. (Kyodo)

The police conducted an on-site inspection of the site to check the safety practices taken there.

Removal of the girder is expected to take place on Friday or later as police continue their investigations and consider charging those found responsible with professional negligence resulting in death.

The roughly 65-meter-long steel frame, which weighs around 140 tons and was intended to form the foundation of the elevated roadway, slipped from a height of some 9 meters, the police said.

The employees were shifting the steel frame to a different position when the incident occurred, according to the Shizuoka National Highway Office.

As a safety measure, the road below the platform had been closed to traffic. As such there were no cars or pedestrians in the vicinity.

"We have heard that many people have been injured. We take this incident seriously and we are very sorry," said an official at Namura Shipbuilding Co., which is part of a consortium that won the contract for the construction work.

The elevated bypass is being installed to alleviate traffic congestion, according to the highway office. The bridge is slated to open in the spring of 2026.

In response to the incident, the Ministry of Land, Infrastructure, Transport and Tourism ordered the temporary suspension of elevated road projects it has commissioned. It is not yet known when work on the suspended projects will restart.