A group of medical workers have been dispatched to the township to conduct further checkups of residents, according to Huang.

The township of Dongtang, which neighbors Danxia Mountain, a World Heritage site, is famous for its rich mineral resources.

The township has the country's largest producer of lead and zinc and a number of mineral refinery plants.

"The surrounding environment is getting worse following the operation of some large mineral refinery plants in recent years," said Liu Hongdai, 59, a resident of Dongtang.

"There is a lot of smoke rising at night from such plants."

Three of Liu's granddaughters have been diagnosed with excessive lead in their blood. The worsening environment has also led to reduced grain production in recent years, according to Liu.

"Some crops and vegetables can hardly be planted here," Liu told the Guangzhou-based Yangcheng Evening News.

Lead poisoning cases have been frequently reported in recent years across the country, with 16 people being punished in connection with a lead pollution incident in Guangdong and a number of battery plants in Shanghai being ordered to close operation over pollution concerns last year.

More than 200 villagers and students near Heyuan Sanwei Battery in Heyuan, Guangdong province, tested positive to having excessive blood-lead levels in May last year. Investigators found that local government and relevant authorities had failed to carry out strict supervision of the company's production and operations.

In Shanghai, some 30 children in Pudong Kangqiao Industrial Zone were diagnosed with excessive lead in their blood in September last year. Shanghai Johnson Controls International Battery has been identified as the major lead emitter in the zone and ordered to suspend production, municipal government sources said.