At least five people were killed Thursday and 11 others were injured in a chemical plant explosion in the central Japanese prefecture of Mie, public broadcaster NHK reported.

The precise cause of the blast, which occurred at the factory Mitsubishi Materials operates in the town of Yokkaichi, some 300 kilometers (185 miles) southwest of Tokyo, has not yet been determined.

All five of those killed were men, according to police, who said the injured have been hospitalized.

Authorities said the persons who died belonged to another company contracted by Mitsubishi Materials and were doing maintenance work at the time of the blast.

Firefighters were notified of the explosion just after 2:00 p.m. by those responsible for the plant.

The shock wave from the blast completely destroyed roughly 10 sq. meters (105 sq. feet) of one wing of the factory, which makes silicon for semiconductors.

Police and firefighters are investigating the causes of the explosion. EFE