About 60 tons of coal tar has contaminated a river in northern China and is threatening to pollute a reservoir which supplies water to a city of 10 million, state media reported Wednesday. A truck carrying the chemical overturned on Monday afternoon in Shanxi province, causing the sticky liquid to spill into the Dasha River, Xinhua news agency reported.

The oily slick, moving at about one kilometer per hour, was approaching the Wangkuai reservoir in neighboring Hebei province, which is about 70 kilometers (43 miles) from the accident scene, it said.

The reservoir is one of two key reservoirs that supplies water to the city of Baoding with a population of more than 10 million.

Workers have set up nine dams and poured 10 tons of active carbon into the river in an attempt to stop the spill from spreading further, Xinhua said.

The report did not say whether anyone had been sickened by the contaminated water.

Industrial pollution of China's waterways was thrown into the global spotlight last November when a chemical factory explosion in the northeastern province of Jilin released 100 tons of benzene and nitrobenzene into the Songhua river.