China suffered its worst industrial accident in a year yesterday when an explosion killed at least 68 people and injured more than 120 at a factory in China that makes wheels for US carmakers, including General Motors.

The blast in the wealthy eastern province of Jiangsu occurred around 7.30am in Kunshan city, about an hour’s drive from Shanghai, after an explosion ripped through a workshop that polishes wheel hubs.

A preliminary investigation suggested that 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 press conference, describing the incident as a serious safety breach.

Several officials from the firm have since been detained, the government said. State news agency Xinhua said five company representatives were held by authorities.

Survivors with charred skin were seen being wheeled into ambulances, as residents recalled hearing the explosion from two kilometres away. At the site of the blast, television images showed wrecked walls and heavy machinery that was hurled through windows.

“We heard a really loud blast at about 7am so we rushed out of our dormitories,” said Zhou Xu, a 26-year-old working at a plant across the site.

“First the ambulance came, then as the news surfaced in the media, many families – especially the wives – rushed to the site to see if their husbands were okay.”

A security guard from an adjacent factory, who declined to be named, said the impact from the explosion was so great that it shattered the windows of his guard house, located about 500 metres away from the site of the blast.

Images online and on state television showed large plumes of black smoke billowing from a white low-rise building. Many of the injured, who appeared badly burnt in scorched clothing, were shown waiting to be stretchered on to trucks, public buses and ambulances.