The director of the Shaoguan city smelting works, Zhang Weijian, has been suspended for investigation, said the semi-official China News Service.

Tens of thousands along the Beijiang river in Guangdong province were without potable water after the smelting works last week released excessive amounts of cadmium, which can cause neurological disorders and cancer.

According to the China News Service, staff at the factory breached safety rules by using just one day instead of three days to carry out cadmium waste treatment work, causing over 1,000 tons of the toxic discharge to spill into the river.

"During maintenance work, some staff had wanted to cut short the treatment time of the waste water, therefore, high density cadmium-containing effluent that was way above (safety) standards was discharged," the report said.

Authorities on Friday poured iron and aluminum polymer into the upper reaches of the river at the city of Yingde to induce the cadmium to settle at the bottom of the river.

"The move is expected to ensure a safe water quality at the lower reaches of the river," Xinhua news agency said in a separate report Saturday.

Officials this week had lowered a dam gate and released water from reservoirs upstream in Beijiang to try to slow the flow of the slick and dilute it as it headed towards the metropolis of Guangzhou.

Local environmental protection authorities have said the toxic discharge has caused the cadmium level in the river at Shaoguan to surge nearly 10 times safety levels, seriously affecting water quality in the lower reaches.

The toxic spill was China's second in as many months after a benzene slick from a factory in northeast China cut tap water to millions of city-dwellers for four days last month.

The two spills have focused attention on water pollution in a country where millions still lack safe drinking water and most rivers are polluted by industrial and human waste.

State media reports said data collected from monitoring points along the Beijiang river suggested that the density of cadmium has been steadily dropping, but residents living upstream in Yingde city's outlying rural areas said Friday their tap water supply has been cut.

In some villages, tens of thousands of residents were relying on water supplied by fire engines, residents told AFP.

Much of the agricultural produce from Guangdong's countryside is exported to neighbouring Hong Kong and Macau.

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