Four people were injured in an explosion Tuesday at the Sakai Chemical Industry Co. Ltd. chemical plant in Iwaki, Japan.

Officials told Kyodo News that the blast happened at about 7:45 a.m. and that three people received burns and one experienced minor injuries during the incident. An English language report noted that the facility manufactures zinc oxide and zinc powders used in the cosmetics and paints industries.

Fire and law enforcement agencies have opened an investigation into the cause of the explosion, according to Reuters.

18 people were inside the plant when the incident occurred, Kyodo News said. No chemicals or gases were released by the blast.