BEIJING (AFP) - Authorities in north China have shut down a smelting plant blamed for the lead poisoning of more than 600 children, after villagers complained the facility was still in use, state media said Tuesday.

Tests have shown that at least 615 children out of 731 living in two villages near the plant in Shaanxi province's Changing township have excessive lead levels in their blood.

Authorities ordered the plant to suspend lead and zinc operations nearly two weeks ago, but angry villagers stormed the smelter Monday and complained it was still producing coke, the official Xinhua news agency said.

One villager quoted in the report said workers had been told not to wear uniforms so as to be less obvious, and added that lights were on in workshops until midnight every day.

The mayor of Baoji city, to which Changing belongs, said coke production had now been stopped.

"Now we've closed down the plant, we won't allow it to open again until it has been proven it will not harm villagers," Dai Zhen she was quoted as saying.

On Sunday, Xinhua quoted Han Qinyou, head of an environmental protection monitoring station where the smelting plant is located, as saying the air near the plant was found to contain high lead levels.

The lead levels in the blood of the children tested ranged from 100 milligram's to more than 500 milligrammes per litre, compared with normal levels of between zero and 100 milligram's. A total of 166 have been hospitalized.

A reading of more than 200 milligram's is considered hazardous, with children more vulnerable to lead poisoning which can harm the nervous system.