HARBIN - A blast occurred Friday morning in a workshop in Northeast China's Heilongjiang province, but details of casualties were not immediately known, witnesses and the local government said.

The explosion happened at a plant that produces heat preservation materials in Limin township, Hulan district, located about an hour's drive from Harbin's city center.

A witness who drove past the scene said he heard a bang and felt tremors. "Later, I heard the sirens of fire engines and ambulances," he told Xinhua over the phone.

An official with the local government in Hulan district confirmed the information.

He said casualties and the extent of the damage were not immediately known.