The mishap took place yesterday when truck, carrying 25 tonnes of highly hazardous crude benzene, broke through the guard rails of a bridge and plunged into the Fenhe River in Xinjiang County, Yuncheng City, they said.
Benzene is a colourless carcinogenic compound used to manufacture plastics. It is known to damage blood production in humans.
The tank was pulled ashore yesterday afternoon after the benzene inside was transferred into another tank, removing a potential major pollution source for four counties downstream, the city government said.
Local authorities in the three counties downstream have built 31 lines of defence with activated carbon to absorb leaked chemical and prevent it from flowing into the Yellow River.