At least five people have been killed in an explosion at a chemical factory in central Japan, police say.

日本中部一家化工厂发生爆炸，至少5人丧生。

The blast occurred at a plant run by Mitsubishi Materials in the town of Yokkaichi in Mie prefecture.

Maintenance crews were working on a heat exchanger used in the production of silicon products when the blast happened, a spokesman at the plant told the AFP news agency.

At least 12 people are reported to have been injured.