Investigations began Thursday on an explosion at the Nagoya ironworks of Nippon Steel Corp. after the fire caused by the blast was extinguished early in the morning.
The blast, in Tokai, Aichi Prefecture, occurred Wednesday in a tank containing coke oven gas. Fifteen people were injured in the explosion, which was so powerful it smashed all the glass in a two-story office building about 200 meters away.
About 60 inspectors from the police and fire departments began their work after Nippon Steel confirmed it was safe to investigate the site.
After the incident the firm said a halt in operations could affect production by its manufacturing clients.
Speaking at a news conference, a Nippon Steel official said production could be hit if the manufacturing of parts is suspended for three days or longer.
The Nagoya ironworks supplies steel products to up to 300 firms, including Toyota Motor Corp., Honda Motor Co., Mitsubishi Motors Corp., Suzuki Motor Corp. and various electronics makers.
Nippon Steel officials said they can transfer the production of some steel products to other facilities but cannot do so with certain types of high-grade products for Toyota and other manufacturers.
The explosion occurred around 7:40 p.m. in the 50-meter-high tank, and the fire it ignited was finally brought under control at 3:26 a.m.
