A chemical plant suspected of causing lead poisoning in more than 300 children in Hengdong county, Central China's Hunan Province, was shut down Saturday, said the county government.

One local official, however, contended that the results might come from the children "biting pencils."

China Central Television (CCTV) reported Saturday that blood tests on more than 300 children in Dapu township,  Hengdong county found excessive lead levels, a sign of heavy metal poisoning.

The lead density in the children's blood all exceeded the national standard of 100 micrograms per liter for children, with some reaching as high as 501 micrograms per liter, which indicates severe poisoning, the report showed.

Local residents suspect that nearby chemical plant Meilun Chemical Materials Ltd, which discharged untreated particulates and waste water into the Xiangjiang River, is responsible for the pollution.

The county government announced Saturday an investigation into both the company owner and the local environmental protection bureau.

Special teams were sent to inspect pollutant discharges from other Dapu enterprises, examine the poisoned children and distribute milk and medicines.

The CCTV report revealed that officials with the local government and environmental protection bureau claimed that management and monitoring indices had reached national standards.

Su Genlin, head of Dapu government, said that children could get excessive lead levels from "biting pencils."

Excessive amounts of lead in the blood could harm the neural and reproductive systems and cause high blood pressure and anemia. In severe cases, it can lead to convulsion, coma and death, according to the Xinhua News Agency.

Some local children that showed excessive amounts of lead shared common symptoms of stomachache or growth retardation, the CCTV report showed.

Eleven-year-old local boy Nie Yilong, who showed high blood lead densities of 248 micrograms per liter, is shorter and thinner than the reference height and weight of those at the same age. Nie's aunt told CCTV that the boy has a "bad memory and is slow-witted."

Lab results showed that dust on the windowsill of local villager Chen Chun'e's house near the chemical plant contained 7,780 micrograms of lead per kilogram, which is 21 times the standard allowed for residential land.

Lead poisoning has been reported in many Chinese cities in recent years and most victims were children. In August 2009, a smelter in Shaanxi Province was closed as its discharges left 851 children ill with lead poisoning, Xinhua reported.