Several factories were shut down in China after children were found to be suffering from lead poisoning, underlining the environmental and health costs of China’s rapid economic development, according to AFP.

High levels of lead were found in the blood of children living near the industrial park. China Youth Daily reported that a higher-than-normal level of lead was found in a boy’s blood stream. Almost 15 children were reportedly suffering from lead poisoning. Exposure to lead can cause nausea and body pain, heart and kidney damage and can harm fertility, according to the US Center for Disease Control.

State media downplayed the incident and said that the 12 factories were only closed temporarily for investigation. Jian’s local government told AFP that there was no evidence of lead leakage.

Chinese activists are protesting against the country’s economic development at the cost of the environment. Beijing is one of the world’s most polluted cities. Violent protests also erupted against the construction of a heavy metals plant in the city of Shifang, in Sichuan province.