BEIJING, Dec. 7 (Xinhuanet) -- The head of national work safety watchdog vowed Tuesday to "sternly" punish those responsible for a chemical plant explosion in northeast China's Jilin Province, which caused toxic leakage into the Songhua River, a main water supply source in the area.

    Li Yizhong, director of the National Bureau of Production Safety Supervision Administration, pledged a thorough investigation in the explosion and the ensuing toxic spill in the river.

    Li, who headed an investigation team set up by the State Council on Tuesday to probe the accident, promised to seriously deal with those enterprises, departments and individuals held responsible for the accident.

    "Anyone, who were found guilty of dereliction of duty, will be harshly dealt with," he said, "those who break the law will be handed over to the judicial departments."

    "People who are found to have provided false information to investigators will also be punished severely," the official said. "Any move trying to cover up the cause of the accident and any passive attitude toward the probe are deemed deception and a defiance of law."

    Meanwhile, he urged all chemical plants and central state-owned enterprises throughout the country to draw lessons from incidents, noting that "a heavy fine is far from enough."

    Effective precautions should be made to prevent similar accidents from happening again, he said.

    The Jilin Shuangben Chemical Plant blast on Nov. 13 killed five, left one missing and injured more than 60 others.

    The explosion caused the spill of a large amount of benzene, a poisonous substance into the Songhua River, forcing Harbin, capital of neighboring Heilongjiang Province, to cut off water supply to 3.8 million citizens for four days, something never experienced by a big city.

    The toxic spill also caused great concerns in neighboring Russia, which borders the river.

    Heilongjiang has intensified monitoring of water quality along the Songhua River as the 150-km pollution spill belt flows further downstream toward Jiamusi, its second largest city in the river's lower reaches.

    Jiamusi, with more than 2 million people, has closed down No. 7waterworks out of the fear that its water source might be contaminated by the pollution slick, whose front was already drawing near its Dalai Town Tuesday morning, said Mayor Li Haitao.

    The investigation team will probe the cause of the blast and why there were no preventative measures in place to prevent the benzene from being discharged into the Songhua River.

    An earlier report said that Yu Li, head of the Jilin branch of China National Petroleum Corporation (CNPC), was removed from his post.

    Two other officials, who allegedly held direct responsibility for the plant explosion, were also dismissed.

    Besides, Xie Zhenhua, head of the State Environmental Protection Administration (SEPA), China's environmental watchdog, resigned after the accident, becoming the highest-ranking Chinese official to resign for an environmental incident. Enditem