The poisoning of the waterway, a tributary of China's longest river, the Yangtze, threatened water supplies in the cities of Zhuzhou, Xiangtan and the provincial capital Changsha.

Jiang Yimin, head of the Hunan province environmental protection agency, said on Monday that cadmium levels in the Xiangjiang River were still "one or two times" above national standard, but did not represent an immediate public health hazard, according to the China Daily.

"Drinking water for households is safe due to timely emergency measures," Jiang was quoted as saying.

But the provincial environmental administration said just on Sunday that cadmium levels in the river were still 22 to 40 times above standard, the China Youth Daily reported.

"Though the government has made some progress in cleaning up the Xiangjiang river after the accident, this newspaper has learned from local officials that the contamination continues and water pollution is still past the safe standard," it said.

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.

Weeks before, a separate cadmium spill in the Beijiang River forced authorities to turn off tap water to tens of thousands of people in southern Guangdong province.

In November, an explosion at a chemical plant in northeast China poisoned drinking water for millions and sent a poisonous slick heading towards Russia.

An estimated 70 percent of China's rivers are contaminated by pollution, raising serious questions about the cost of the country's economic boom.

Hunan officials, including Jiang, met on Friday to discuss whether to shut water supplies to the three cities, and decided not to because "water quality was stable" and for fear of sparking public panic, the newspaper said.

The cadmium was believed to have come from the more than 200 chemical factories upstream of Zhuzhou that were pillars of the local economy, it said.

Toxic waste water from the factories, nearly all untreated, was still flowing into the river as of Sunday, the report said.

The Xiangtan government knew the Xiangjiang was contaminated with cadmium as early as June or July of 2004, Wang Guoxiang, a local legislator, told the newspaper.

"Some local authorities only pay attention to the environment when problems arise, and sometimes then they still respond carelessly," Wang said.

The China Daily said that the government had ordered chemical factories along the river to stop production.

But a factory worker told the China Youth Daily that at least one chemical plant had not shut. A worker involved in the clean-up project that released the cadmium into the Xiangjiang said the crisis was just a drop in the bucket in the heavy pollution of the area.

"It's not just the water that's polluted, look at all the smoke in the air. Even wearing a mask is no use," he said.