Four workers were killed and nine others were injured Monday afternoon in a blast at a petrochemical plant in northwest China's Gansu Province, according to the provincial bureau of work safety.

The accident occurred at 3:32?PM at an anilin device of the Lanzhou Petrochemical Co. Ltd., a subsidiary of PetroChina, when workers were dismantling apparatuses from the device. Four migrant workers died on the spot and nine others were injured during the explosion.

The nine injured, including four severely wounded ones, have been rushed to a local hospital for medical treatment.

Investigation into the cause of the accident is under way.

(Xinhua News Agency May 30, 2006)