Authorities in the south-western Chinese province of Yunnan have discovered a number of children in Heqing County with excessive levels of lead in their blood caused by illegal gold processing operations.

The children were diagnosed following a crackdown by the local environment protection department on illegal metallurgy activities that were using cyanide to extract gold from ore, reports Bloomberg.

Soaring gold prices have led villagers in the county to process ore in their homes, generating lead fumes and poisonous solid waste, the Heqing Government said.

Data from the Ministry of Environmental Protection shows that more than 4,000 people in China, including 2,000 children, were poisoned by lead last year.