A clean-up accident allowed industrial chemical cadmium, which can cause neurological disorders and cancer, to flood out of a smelting works and into the Xiangjiang River in Hunan province on January 4, Xinhua news agency said.

The river supplies tap water to residents in the provincial capital Changsha, which has about six million people, and nearby Xiangtan city, which has 700,000 inhabitants.

Officials told AFP they have taken emergency measures and residents were not in danger.

Local authorities have blocked off the spill and are trying to neutralise the cadmium slick with different chemicals and dilute it by releasing water from a dam.

"Even though this pollution incident is not over, there's no impact on residents' lives," said an officer surnamed Zhou at the Changsha city government's office.

"The water being supplied by the water treatment plants is still up to standard."

A Xiangtan government spokesman gave similar assurances.

Xinhua said the amount of cadmium in the river reached 25.6 times above safe levels at its peak but had dropped to 0.14 times by Saturday.

Officials said they did not have to shut off water supplies as measures they took were effective and water treatment plants were able to filter out the pollution.

Local residents, including hotels in Xiangtan, also said there was no disruption to their water supply.

However several residents said they did not know about the spill, which was not reported on Xinhua, the main government mouthpiece, until Saturday night. It was not clear whether local media had reported it earlier.

The incident follows a cadmium spill in southern China's Guangdong province which cut tap water supply to tens of thousands of people for more than a week last month.

In November, a toxic benzene slick from a factory explosion in northeast China polluted the Songhua River and cut tap water to millions of city-dwellers in Heilongjiang province.

The 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.

The latest accident occurred due to human error, Jiang Yimin, director of Hunan province's environmental protection bureau was quoted saying.

The Zhuzhou Water Conservancy Investment Co. Ltd. caused the spill while it was trying to clear silt at the Xiawan Harbor in Zhuzhou city, which is where the smelter is located and is upstream from Xiangtan and Changsha, Jiang said.

Polluted water from the smelter is normally allowed to flow out of the harbor, but the clean-up company diverted the flow while the project was in progress.

The cadmium-contaminated water collected in two lakes which then overflowed into the river, Xinhua said.

In a separate incident, Xinhua said six tons of diesel oil flowed from a frozen pipe that broke into the Yiluo River in Gongyi city, central China's Henan province Thursday.

No further information was given. Henan officials on Saturday lifted a pollution warning on the river after water quality returned to normal, Xinhua said.

Xinhua on Sunday also said the government would invest 26.6 billion yuan (3.28 billion US dollars) to control pollution in parts of the Songhua River in Heilongjiang, Jilin and Inner Mongolia provinces over the next five years.

More than 90 percent of the people living in the Songhua River valley are expected to have clean drinking water by 2010, according to the plan.

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