Local government has increased water discharge of the reservoirs on the upper streams to help dilute the pollution in the Xinqiang River, and tap water supply for about 80,000 residents in the county was expected to resume the next Tuesday, Tong Kangning, secretary of the Yueyang County Committee of the Communist Party of China told Xinhua on Sunday.

The Xingqiang River was found contaminated with arsenide from a waste water pond leakage at a chemical plant 50 kilometers upstream when the local environmental monitoring center conducted a routine examination of water quality in the River.

A task force from the State Environmental Protection Administration (SEPA) visited the Xinqing River, the source of a local waterworks, on Tuesday afternoon.

The chemical plant had been shut down, however, the waste water might threaten the Dongting Lake, the country's second largest freshwater lake and a major drinking water source for Hunan, which is less than 20 km from the polluted river, said Zhang Zhimin, deputy director of the SEPA's quick-response center for emergencies.

"Though the lake water is safe to drink, its arsenide content is higher than the normal lever," said Zhang, adding local environment department has been required to step up monitoring on the water quality of Dongting Lake.

Local authorities has issued a circular to warn residents against drinking tap water and provide safe drinking water for them.

According to environmental experts, arsenic trioxide is a kind of white powder which is very poisonous. People poisoned with arsenide may feel sick, vomit and get stomach pain. It may lead to coma, twitch or even death.

Chronic intake of arsenide may cause damages to people's liver and kidney or lead to lung cancer and skin cancer.