The number of children sickened from lead poisoning has risen to more than 600 in a northern Chinese province where authorities shut a smelter earlier this week thought to have caused the contamination, state media reported.

More than 80 percent of the 731 children living in the two villages near the Dongling Lead and Zinc Smelting Co. in Shaanxi province have tested positive for lead poisoning, nearly double the number reported earlier this week, the official Xinhua News Agency reported late Thursday.

Families who lived near the factory began bringing in sick children to hospitals and clinics in July and blamed the smelting factory for contaminating nearby soil, air and the area's water supply, the report said.

Local officials say they plan to relocate all 581 households living with 500 meters (1,600 feet) of the factory within the next two years, the report said.

Of the sickened children, 166 will be hospitalized and the remainder will receive at-home treatment to remove the lead from their bodies, according to Xinhua.

A spokesman for the local government, surnamed Wang, confirmed the new numbers and said the case was under investigation but refused to comment on whether sicknesses are linked to environmental pollution caused by the smelting company. He refused to give his full name as us common among Chinese officials.

Factory accidents and chemical leaks are common in China and are often blamed on lax enforcement of environmental regulations and safety rules and poor worker training.

Lead poisoning can damage the nervous and reproductive system, cause high blood pressure, anemia, memory loss, and in extreme cases cause victims to fall into comas and die.

China's waterways, especially its major rivers, are dangerously polluted chemicals after decades of rapid economic growth and poor enforcement of pollution controls.