Water pollution in Shuyang County, east China's Jiangsu Province, has caused close of the county's water supply system in urban area since Monday, affecting 200,000 local residents, government sources said on Tuesday.

Harmful substance in the county's water supply plant was detected at 3:00 PM Monday. The substance was identified as ammonia and azote and the amount is 28 mg per cubic meter.

This is much higher than the standard for drinking water, according to local environment watchdog. Initiate investigation shows that the pollution was caused by industrial waste water of a chemical plant located on the upper reaches of a local river.

In a bid to provide drinking water for the residents, the local government has put into use of 33 wells, which fetch water from unpolluted ground water sources.

Meanwhile, the county has poured water from Hongze Lake into local water sources to dilute the pollution substance.

Further efforts and investigation on the accident is still under way.

(Xinhua News Agency July 4, 2007)