China says a fuel spill into a tributary of the Yellow River has reached an important reservoir, raising fears that the drinking water of millions of people may become contaminated.

According to state news service Xinhua, diesel spilled from a broken pipeline into the Weihe River has reached the Sanmenxia reservoir on the Yellow River. Dams on this reservoir have been closed since 3 January in an attempt to stop the pollution reaching the Xiaolangdi Reservoir which supplies drinking water to the cities Kaifeng and Zhengzhou.

Earlier, reports suggested that the 150 cubic meters of diesel that leaked from a China National Petroleum Corporation pipeline were under control.

Xinhua says Zhengzhou city is home to 2.4 million people. If the diesel spill makes the Yellow River supply undrinkable other reservoirs can provide the city with water for 50 days, say officials.