TSU, MIE PREF. – Five people died and 12 were injured Thursday in an explosion at a Mitsubishi Materials Corp. plant in Yokkaichi, Mie Prefecture, police said.
Mitsubishi Materials said that a heat exchanger outside the plant’s No. 1 facility exploded at around 2:10 p.m. during cleaning work.
It is possible that the explosion was caused when a chemical agent inside the heat exchanger was exposed to air, the company said. About 20 people were taking apart and cleaning the equipment at the time of the accident.
The victims were involved in the operation, some as supervisors, it said. The explosion did not trigger a fire.
According to the fire department, three of the five killed were Mitsubishi Materials employees and the other two were workers from outside the company. The seriously injured man was taken to Mie University Hospital in Tsu, the capital of the prefecture, by helicopter.
The factory, located in an industrial district in Yokkaichi, produces silicone that is used in semiconductors for personal computers. The material is produced through a reaction of trichlorosilane, a compound made from metallic silicon, with hydrogen gas.
The plant, which operates 24 hours a day, has an annual production capacity of 2,800 tons, including that of the No. 2 facility. The company is legally required to carry out inspections three times a day.
Some 70 percent of the plant’s products are supplied to major silicon wafer manufacturer Sumco Corp.
The Fire and Disaster Management Agency sent officials to the plant to investigate the cause of the explosion.