Five men and one woman sustained slight injuries in an explosion Wednesday morning at Rinnai Corp.'s factory in Aichi Prefecture, police said.
A fire caused by the 10:15 a.m. explosion at the company's factory in the town of Oguchi was extinguished around 20 minutes later, they said.
Investigators said the explosion occurred in a laboratory on the first floor of the five-story building. A gas leak related to the examination of a new product made by the firm may have caused the explosion, police said.
Rinnai, based in Nagoya, is the nation's leading manufacturer of gas appliances such as stoves, rice cookers and bath heaters.