Some of them had lead in their blood several times higher than safe levels, according to the report.

So far there was no definitive explanation for the cause of the sudden wave of poisoning but a general consensus blamed a local smelting factory, the Huashan Daily newspaper reported earlier.

Late last month the Hui county government ordered the factory to close and move to a safer location, according to the paper.

CNS described the plant as a virtual ecological time bomb, pumping out polluted waste water and emitting dark fumes and thick clouds of dust.

County officials told AFP many villagers had gone to Xian city in neighboring Shaanxi province to have their blood tested, trusting the more modern facilities there.

"After the news broke about 1,000 people had their blood lead levels tested," an official said.

"We haven't got complete statistics yet so we still can't say how many have been poisoned."

Lead poisoning can have a variety of adverse effects, from nausea and insomnia to comas and impaired mental development in children.

China's economic development offers the people of many regions a stark choice between a clean environment and rapid growth.

China's cities have some of the worst air pollution in the world, while its polluted waterways are already exacerbating existing water shortages in many parts of the nation.

Related Links
Our Polluted World and Cleaning It Up