Chemical plant blast kills at least 5 workers in Japan

TOKYO -- An explosion at a chemical factory in central Japan on Thursday killed at least five workers and injured 17 others, authorities said. 

Investigators suspect a chemical reaction involving hydrogen caused the blast at metal and chemical company Mitsubishi Materials Corp.'s Yokkaichi plant, about 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.

Japanese media reported the plant, which made materials for semiconductors. was in the process of being dismantled when the explosion occurred. 

Police said five workers died. Fire department officials said that 17 people were taken to hospitals. 

The dead and injured were all believed to be workers at the factory.

The fire has been extinguished, a fire department official said.