A nine-kilometer slick of crude oil that spilled from a storage tank into the Zhouhe River in northwest China's Shaanxi Province, has been put under control from further expanding, local officials said Sunday.

An official with the Zhidan county government said a clean up crew of over 600 have taken back about 90 percent of the four tons of crude oil spilled into the Zhouhe River, a tributary of the Luohe River which flows into the Yellow River, the country's second longest.

It's known that oil spill occurred at around midnight Friday when a storage tank burst, leaking out over 10 tons of crude oil, about four tons flew into the Zhouhe river. The oil tank belongs to the Yongning Drilling Company from the county of Zhidan.

Workers were cleaning the another tank at the time, said company officials.

A clean up crew of over 600 were immediately dispatched to the accident site and built six dams to prevent the slick of crude oil from further expanding. The polluted belt was controlled within nine kilometers, according to local government.

The cause of the oil spill is being investigated.

(Xinhua News Agency August 14, 2006)