Three companies in Shanghai are being questioned for causing lead poisoning in at least 49 children.
A battery manufacturer, an auto-parts maker and a recycling company were found responsible for the elevated levels of lead in the children's blood, the Shanghai Daily reported Sunday. All three businesses have been shut down.
Of the 1,300 children living in Pudong area of the city who had their blood tested last September last year in routine checks for kindergarten and primary school admission, 49 were found to have lead in their blood.
The affected children were mainly between the ages of one and three. All of them have received treatment but three are still in hospital.
An investigation conducted by environmental and health authorities said the children became ill after being exposed to high levels of lead in the environment.
Dirt containing lead entered the children's bodies through the digestive system, experts found.
"In addition to lead exposure from the environment, most of the children with excessive blood lead used a prickly heat powder that contains lead chemicals. The prickly heat powder was made based on a folk prescription," said Yan Chonghuai, a doctor from the city's Xinhua Hospital.
The report said the battery maker discharged excess lead into the air as it expanded production without government permit.
The auto parts manufacturer was found to have used lead on its production lines without authorisation while investigators found excessive levels of lead and zinc in the soil inside the recycling plant.