A large amount of diesel oil that leaked from a key pipeline of China National Petroleum Corporation (CNPC) polluted the Wei River in Weinan, north China's Shaanxi province, China News Agency reported Saturday.

The accident happened on the pipeline that connects Lanzhou in northwest China’s Gansu province to Zhengzhou in central China’s Henan province on December 30, 20009. The leaked oil first entered into Chishui River, a tributary of Wei River.

A section of river spanning 33 kilometers reported pollution, Shaanxi TV said. It was not clear how many tons of diesel oil leaked.

CNPC, the country's largest oil and gas producer, and local government mobilized over 700 people to cordon off the contaminated area and start clean-up actions. The cold temperatures helped rescue workers collect the leaked oil, local media reported.

Chinese Vice-Premier Li Keqiang urged the local government to prevent the oil from entering the Yellow River and ensure the safety of drinking water. Eleven barriers were set up downriver of the Wei River.

China News Agency reported preliminary investigation showed the pipeline was damaged by construction conducted by a third party. No details were given.