YAN'AN, Shaanxi - Oil spilled from a cracked underground oil pipeline has polluted a section of a river in Northwest China's Shaanxi province, local authorities said Tuesday.

The severe impact of a rain-triggered landslide cracked the pipeline, located in Zichang county, Yan'an city, at 4:58 am Monday, causing nearly a ton of crude oil to flow into the Haojiachuan River, a seasonal river, according to the city's publicity department.

Yanchang Petroleum Group's Pipeline Transportation Company, the operator of the pipeline, immediately turned off the oil valve after the leakage was detected.

More than 3,000 people have joined clean-up efforts, and 18 floating dams have been built to curb the spread of oil and remove it from the river.

The publicity department added that the spill had been contained within 21 km of the leakage point as of 5 p.m. Monday.

The oil-tainted river is not a water source for local residents, as it usually runs dry when precipitation drops in October.

Ma Hongyu, vice mayor of Yan'an, urged local authorities and the oil company to work together to stop the oil from spreading and remove pollutants from the river before 6 p.m. Tuesday.

Heavy downpours have swept across a large swath of Shaanxi province since last week, killing 27 people as of 8 a.m. Monday, according to the Department of Civil Affairs in Shaanxi province.