Cadmium levels have been 10 times normal in the Shaoguan city section of the North River running across the booming southern province of Guangdong, the government-run Guangzhou Daily said on Wednesday.

A hotel receptionist in Shaoguan city, with a population of half a million, said water was turned off on Tuesday from 9 a.m. to 5 p.m.

"But it came back on afterwards," she said by phone.

People who live along the river had been told not to drink the water, the Guangzhou Daily said.

The zinc smelter, China's third largest, has been ordered to stop production on suspicion of water pollution, state television said on Wednesday, citing sources in the plant's home province of Guangdong.

"Due to the situation, the Shaoguan smelter has been ordered to halt production pending adjustments," Shanghai Television reported without elaborating.

"Currently, the polluted water is flowing downstream. The environmental bureau has initially confirmed that this situation arose because the Shaoguan smelter released abnormal amounts of polluted water containing cadmium during equipment maintenance," the station said.

Two officials with Shaoguan's listed parent, Shenzhen Zhongjin Lingnan Non-ferrous Metal Co. Ltd., told Reuters earlier there had been no impact on operations.

Company officials could not be reached Wednesday evening.

EMERGENCY MEASURES

The downstream city of Yingde, with a population of 100,000, would not have to turn off taps as it had switched to a nearby reservoir to draw water, a local government spokesman told Reuters by telephone.

The city had also been rushing in drinking water by road, including by fire engine, the Guangzhou Daily said.

Reservoirs upstream had increased discharges to dilute the pollutants, it said, adding the cadmium density had been declining.

Further downstream, the North River will reach a city of half a million, Qingyuan, which has also launched emergency measures, before it enters the Pearl River Delta.

Cadmium, a metallic element widely used in batteries, can cause liver and kidney damage and lead to bone diseases. Compounds containing cadmium are also carcinogenic.

A petrochemical plant blast in China's northeastern Jilin province in November poured some 100 tonnes of toxic benzene compounds into the Songhua River. Taps were turned off for nearly a week in the downstream city of Harbin, which is home to around 9 million people.

China is building a dam to divert that slick before it runs into Russia's far east city of Khabarovsk through the mostly frozen Amur River, Chinese Foreign Ministry spokesman Qin Gang told a news conference on Tuesday.

The density of nitrobenzene, the main pollutant, had been rising in Fuyuan, the last city within China along the Amur River and where the dam is being built, the State Environmental Protection Administration said on its Web site on Wednesday.