TOKYO (AP) — Authorities and news reports say an explosion at a chemical factory in central Japan has killed at least five people and injured more than 10 others.

Police say the explosion occurred at Japanese metal and chemical company Mitsubishi Materials Corp.’s Yokkaichi plant Thursday afternoon during maintenance.

Fire department officials say 17 people injured from the blast were taken to nearby hospitals. Police say two were dead, while Japanese media including Kyodo News agency put the death toll at five. Conditions of the injured were not immediately known.

Mie prefectural police say investigators suspect a hydrogen explosion caused by chemical reaction when plant workers were rinsing heat exchange equipment at a silicone plant on the complex in Yokkaichi City, about 350 kilometers (220 miles) west of Tokyo.