Investigators suspect chemical reaction involving hydrogen caused the blast at metal and chemical company Mitsubishi Materials Corp.’s Yokkaichi plant, about 350 kilometers (220 miles) west of Tokyo.
The blast appeared to have occurred when plant workers were rinsing heat exchange equipment at the silicone plant during maintenance, according to a Mie prefectural police official, who spoke on condition of anonymity due to department rules.
Police said five workers died. The dead and injured were all believed to be workers at the factory.
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