The youngsters were among 877 people in two villages found to have excessive lead in their bloods in August. Of that figure, 334 were children aged one to 14.

A nearby smelting plant was blamed for the problem.

Each of the 877 persons was further checked to see if they had actually been poisoned by the lead.

"The first group of blood samples involved in the case in August were tested by the Chinese Centre for Disease Control and Prevention (CCDCP), and the blood samples from 62 children were diagnosed as having moderate or severe lead poisoned," Sun Yajun, deputy director of the Medical Emergency Office under Gansu Provincial Health Department, told China Daily on Monday.

Medical experts say 100-249 mg of lead per litre of blood is excessive. They say more than 250 mg per litre is evidence of poisoning.

The children, aged between one and 14, have been receiving medical treatment, the deputy director said.

Yang Jingke, spokesman of the provincial health department, said regulations had been followed.

"In accordance with State standards, people with excessive lead in their blood must be tested by authoritative bodies to see if they have been poisoned. So we asked the CCDCP to test the blood samples for confirmation," Yang said.

Lead poisoning is particularly harmful to children, causing cell problems and growth disorders. However, patients can be cured over time with proper medical treatment, doctors said.

According to the local health department, those villagers suffering from excessive lead in their blood are also receiving treatment.

"We will further test villagers who live in the polluted area," a spokesman said.

The smelting plant has been closed down by the local government. The owner and managers have been arrested, according to official sources.