Six workers were killed and one is missing after a blast at a chemical plant in northwest China's Qinghai Province on Sunday.

The explosion occurred in a dust collection device at a cement production line belonging to Qinghai Salt Lake Haina Chemical Company when 26 workers were on site, said Liu Yunzhou, head of the administration commission of Ganhe Industrial Park in the Xining economic and technological development zone.

Two died on the spot and 12 others were injured. Four of the injured later died in hospital. The other eight are receiving treatment and are described as stable.

Search for the missing worker continues. The cause of the accident is being investigated.

The company started production in 2013 with a daily capacity of 2,500 tonnes of cement.