The Ministry of Environmental protection and the government of Jiangsu province have formed a task force to investigate pollution-related illnesses at Changzhou Foreign Language School.

Among the 641 students examined by hospitals, 493 were diagnosed with diseases and conditions that were related to pollution, including dermatitis, bronchitis and blood abnormalities. Some were even found to have leukemia and lymphoma.

The investigation team will make its results public as soon as possible.

The government of Changzhou has also formed its own team of investigators and said that no violation of the law will be tolerated.

According to the local government, professional testing organizations were hired by the parents and the school in late March to check the quality of indoor air, soil and groundwater. The results showed that all of them met national standards.

Almost all of the school's 2,451 students have attended regularly, except for four who want to transfer, three calling in sick and one leave of absence. Of its 210 teachers, all regularly attend except for three calling in sick.

"Public supervision is welcomed," a notice released by the local government on Monday said. "We'll investigate carefully and deal with the problem according to law."

The school's new campus, which opened in September, was built on a heavily polluted field that had formerly housed three chemical factories. The plants had produced highly toxic chemicals including carbofuran and methomyl.

The factories allegedly buried toxic chemicals near their plants and discharged untreated wastewater into rivers. The soil and nearby groundwater contained organic pollutants and heavy metal pollutants such as chlorobenzene, carbon tetrachloride and mercury.

According to an environmental report, the concentrations of chlorobenzene in the groundwater and soil greatly exceeded normal levels. The level of chlorobenzene in the groundwater was 94,799 times the normal level while in soil samples, it was 78,899 times what it should have been.