Three people were killed and two seriously injured in an explosion at a chemical plant in northeast China's Heilongjiang Province on Monday, a press release from the China National Petroleum Corporation said. A gas tank at the No.2 refining plant of the Daqing Refining & Chemical Company in Daqing…exploded…The explosion also caused a fire, which was put out…The water polluted in the explosion was restricted in company's water treatment facilities, and there was no air pollution at the site, the press release said…The China National Petroleum Corporation has sent specialists to the explosion site to investigate the cause of the accident.