A spill of toxic cadmium into a river in southern Guangxi Zhuang Autonomous Region has been stemmed and there have been no further leakages, according to local environmental authorities.

Flowing water has diluted the cadmium content to safe levels in the reservoir of the Lalang Hydropower Station on the Hechi City section of the Longjiang River, where the contamination originated.

However, pollutants moved downstream and reached the source of nearby Liuzhou City's drinking water, Xinhua news agency reported yesterday.

The cadmium concentration at the Nuomitan Hydropower Station, 56 kilometers from Hechi, was seven times higher than the official limit of 0.005 milligrams per liter as of 10am yesterday, said Gan Jinglin, director of the Liuzhou City Environmental Protection Bureau.

Yesterday's tests also showed that the cadmium concentration on a section of river 16 kilometers from the plant was 0.0041 milligrams per liter, just below the official limit, Gan said.

"However, the rising cadmium concentration means that the pollutants are approaching, and it is still unknown when the concentration peak will occur and how high it will be," Gan said. "We are keeping a close eye on the river's water quality."

Gan added: "The level of the toxic chemical in Liuzhou water sources is still within the required standard and will remain safe for at least four days.

"We are able to treat the tainted water in time, even if the pollution is double the restricted level, to ensure a sufficient supply of safe drinking water."

Liuzhou Mayor Zheng Junkang said the government had made every effort to contain the contamination and had taken emergency response measures, Xinhua reported.

"We have activated a contingency plan to tap into 3.5 tons of underground water reserves in case the original water source is contaminated," Zheng said.

The contamination was detected in Liujiang River last Thursday, 11 days after the Jinhe Mining Co Ltd discharged industrial waste into the Longjiang River, a tributary upstream of the Liujiang River, Xinhua said.

Cadmium is an extremely poisonous metal commonly contained in industrial effluents. An agent designed to promote the clumping-together of pollutants has been dumped into a dam on the Longjiang River so they can be removed more easily.

Production at all seven heavy metal producers along the upstream section of the Longjiang River has been suspended in a bid to curb potential sources of new pollution.

Though the authorities have assured residents in Liuzhou that their water supply is safe and adequate, the spill still caused panic buying of bottled water.