LUOCHUAN, Shaanxi -Some 1,000 tons of oil sludge spilled from a sewage treatment plant has contaminated Luohe River in Luochuan county of Northwest China's Shaanxi province, local officials said on Friday.

The Luohe River is a tributary of the Yellow River, referred to as the "Mother River" in China because it is the water source for millions of people.

Wang Xirong, deputy magistrate of Luochuan county, told China Daily that on Sunday morning, an oil sludge recycling pool at a sewage treatment plant in Yan'an city collapsed, sending some 1,000 tons of oil sludge flowing, with some going into the Luohe River.

The oil spill is the second river pollution incident to hit the province in three months, after the Yellow River was contaminated by a diesel fuel leak in early January.

Zhang Xun, deputy director of emergency office under the Ministry of Environmental Protection, who is leading a team to deal with the incident, has demanded the decontamination be finished within five days.

"We should try every way to stop the contamination source from going out of Yan'an," he said.

Vice-Premier Li Keqiang has instructed local authorities to ensure the safety of the drinking water downstream of the river.

More than 2,000 people were organized immediately after the incident to remove the contamination from the river. Eight floating dams were put in the river to stop the contamination from going downstream, Wang Xirong said.

Wang Hongli, an official in Jiaokouhe town where the sewage treatment plant is located, said the leaking sludge flowed to an apple orchard next to the plant and contaminated the farmland, and then flowed into the valley, which leads to the river.

"At present, the sludge in the river has been effectively controlled and we will make efforts to clean up the contamination in the farmland and valley. We will complete the work within three to five days," the town official said.

In Baishui, Luochuan's neighboring county, where the Luohe River also flows, more than 400 people are ready to intercept any polluting sludge coming from upstream.

Zhao Jingfeng, director of the Luochuan county environmental protection bureau, said results of the water quality test made at the junction of Luochuan and Baishui counties showed no contamination. The bureau will continue testing the water quality once every hour.

The preliminary investigation of the failure at the sewage plant showed that the accident was caused by ground collapse. The investigation is ongoing, Zhao said.

China daily