HARBIN - At least one person was killed in a workshop blast in Northeast China's Heilongjiang province on Friday morning, sources with the local government said.

The explosion occurred around 9 am at Harbin Haoyang Thermal Insulating Material Co, Ltd. 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.

Another witness said he heard a loud bang and instantly saw thick smoke billow out of the factory yard.

An initial investigation indicated that a tank containing one tonne of toxic carbolic acid exploded due to improper operation during equipment commissioning.

Police have cordoned off the scene to keep passengers-by at bay.

Li Chao, the district's work safety chief, said local authorities are discussing ways to handle the chemical leak, which poses hazards to the environment. The situation is under control, he added.