By Michael Bristow
BBC News, Beijing
At least 600 children have excessive amounts of lead in their blood
Hundreds of Chinese villagers have broken into a factory that poisoned more than 600 children, reports say.
Villagers tore down fencing and smashed coal trucks at the lead smelting factory in Shaanxi Province.
Local authorities have admitted that the plant is responsible for poisoning the children. More than 150 were in hospital.
Air, soil and water pollution is common in China, which has seen rapid economic growth over the past few decades.
The villagers broke into the Dongling Lead and Zinc Smelting Company, near the city of Baoji in western Shaanxi on Monday, according to the state-run Xinhua news agency.
About 100 police officers were sent to the plant to restore order.
The villagers are angry because medical tests revealed that at least 600 children under 14 from two villages near the plant have excessive amounts of lead in their blood.
About a quarter of them were taken to hospital for treatment.
Environmental officials from Baoji city government admitted on Sunday that the plant was "mainly to blame" for the children's lead poisoning, according to Xinhua.
Checks found that water, soil and waste from the factory - a major local employer - all met national environmental standards.
But the lead content in the air around the factory was more than six times the level found a few hundred metres away.
The smelting plant has now been closed down.
Local officials had promised to relocate all residents living within a 500m ( 550 yard ) radius of the factory within three years of its opening, but that plan stalled.
Xinhua said only 156 families had been moved; three times that number are still waiting.
Villages are also worried that the new homes are still not far enough away from the plant to prevent their children from getting sick.
Lead is a toxic metal that can get into the air and water supplies.
It can cause a range of health problems, from learning disabilities to seizures. Children under six are most at risk.