Beijing, China ? A chemical spill in a northwestern Chinese river has polluted a reservoir serving 100,000 residents, state media reported on Saturday.

A tanker truck loaded with 25 tons of liquid caustic soda fell into a river on Friday three miles away from the Xuefeng reservoir in the Shaanxi province city of Han-cheng, Xinhua News Agency said.

Local government officials built a dam at the site after the vehicle fell in and ordered residents not to use the water from the reservoir, the report said.