NIIGATA (Kyodo) -- The bodies of four workers missing since Thursday following an explosion at a tunnel construction site in Minamiuonuma, Niigata Prefecture, were located and recovered in a rescue operation Sunday morning, local firefighters said.
The four went missing after the explosion, which occurred at around 10:30 a.m. Thursday around 1.2 kilometers from the entrance of the 2.8-km tunnel under construction. The explosion also injured three other workers who were taken to hospital, local police said.
As the four missing workers were believed to have been in an area around 1.3 km from the tunnel's entrance, firefighters and police launched a rescue operation immediately after the explosion. But the operation ran into difficulties on Thursday night after highly flammable gas was detected in the tunnel.
The rescuers found the bodies of the four inside the tunnel around 1:15 a.m. Sunday but were unable to retrieve them until shortly after 6 a.m. because of the density of the gas.
The four, who were confirmed dead, were identified as Daisuke Kobayashi, 37, Kokichi Koshii, 57, Takafumi Toda, 40, and Masayuki Otani, 39. Kobayashi was an employee of Sato Kogyo Co., a major Tokyo-based contractor undertaking the tunnel construction, and the other three were working for a subcontractor.
The police on Sunday morning searched the office of Sato Kogyo's Hokuriku branch in the city of Toyama in Toyama Prefecture and two other places on suspicion of professional negligence resulting in injury.
The construction company said the seven workers were preparing for the resumption of construction work Thursday morning after a winter break. The tunnel is scheduled for completion by December.
A local office of the infrastructure ministry said earlier the tunnel route had been changed to avoid a geological stratum thought to contain methane gas.
Flammable gas was likely to leak from some strata around the tunnel construction site, an expert said earlier, adding that gas could have built up when several kilometers of the tunnel were closed over the winter months.
