State news agency Xinhua had previously reported that seven people died and one person was missing after the Saturday morning explosion at the Jiapeng biotech company in Shanxi province, citing local authorities.

Later, Xinhua said eight were dead, adding that the firm's legal representative had been taken into custody.

The company is located in Shanyin County, about 400 kilometres west of Beijing.

Xinhua said clean-up operations were ongoing, noting that reporters observed dark yellow smoke emanating from the site of the explosion.

Authorities have established a team to investigate the cause of the blast, the report added.

Industrial accidents are common in China due to lax safety standards.

In late January, an explosion at a steel factory in the neighbouring province of Inner Mongolia left at least nine people dead.