Excessive lead was found in the blood of 84 children in Heqing county of Southwest China's Yunnan province as of 3 pm on Sunday, local authorities said on Sunday evening.

Two children diagnosed with lead poisoning are admitted to a local hospital on Saturday in Heqing county of Yunnan province.

The children were sent to the People's Hospital in Heqing for free medical treatment, the county government said in a statement.

The figure, an increase on the 39 cases reported on Friday, was the result of health checks on children being expanded over the weekend, the statement said.

The toxic element was initially detected in children under the age of 14 during a check conducted by the local health department from July 2 to July 16, the statement added.

The affected children experienced muscular spasms and had been vomiting before their conditions were diagnosed.

"My kid is only four years old. We sent him to the hospital when he was suffering from muscle jerks," said Yang Weihong, the father of a sick child.

It is now 10 days since the children were admitted to the hospital, which has yet to make a statement on their conditions.

"The only thing we know is that our kids have excessive lead in their blood," a local resident said.

According to Yang, the hospital dispenses a liquid medicine and milk to treat the condition.

The children were diagnosed following a crackdown in June by the local environmental protection department on illegal gold metallurgy activities, which can generate lead fumes and poisonous solid waste.

To contain the situation, a clean-up operation has been launched in which the streets are being washed down to reduce the amount of fine particles in the air, the statement said.

An initial investigation found that the children might have inhaled lead fumes discharged from illegal gold metallurgy workshops owned by some villagers, who took to dumping poisonous mineral wastes in nearby fields.

According to the local health administration, over 300 villagers tested positive for excessive lead content in their blood from 1977 to 1992.

Yang, who used to work at a local lead-smelting factory, was also diagnosed with the condition in 1997.

Recalling his symptoms, he said: "It felt like I had to go the toilet all the time."

Excessive lead content can damage the nervous and reproductive systems, as well as cause high blood pressure and anemia. In severe cases, it can lead to convulsions, coma and even death.

Although the local government closed most smelting plants in the 1990s to protect the environment, some villagers opened illegal gold metallurgy workshops as the price of lead rose in recent years, according to a report by Xinhua News Agency.

Since last year, the country has faced a rising number of incidents involving heavy-metal pollutants. In one of them, more than 1,350 children under the age of 14 were diagnosed with excessive lead in their blood in four villages near a smelting plant in Wugang of Central China's Hunan province.

In Jiyuan, which has the largest concentration of lead smelting in Henan province, the government is planning to move 15,000 residents away from the threat of lead poisoning after nearly 1,000 children were diagnosed with excessive lead in their blood, at a cost of 1 billion yuan (US$147 million).