China suffered its worst industrial accident in a year on Saturday when an explosion killed at least 69 people and injured more than 120 at a factory that makes wheels for U.S. carmakers, including General Motors.

The blast in the wealthy eastern province of Jiangsu occurred around 7:30 a.m. in the city of Kunshan, about an hour's drive from Shanghai, after an explosion ripped through a workshop that polishes wheel hubs.

A preliminary investigation suggested the blast at Kunshan Zhongrong Metal Products Co Ltd. was triggered when a flame was lit in a dust-filled room, the local government said at a news conference, describing the incident as a serious safety breach.