(CNN) -- Two plants in Shanghai -- including a unit of an American company -- were ordered to suspend production after children in the vicinity came down with lead poisoning, government authorities said Friday.
"A small amount of children living in Kangqiao (eastern Shanghai) area were found to have excessive levels of lead in their blood in early September," according to a statement from the Shanghai Environmental Protection Bureau.
According to the state-run Xinhua news agency, 25 children were sickened, 12 who were hospitalized.
The local government responded on Wednesday by ordering the suspension of plants owned by Xinmingyuan Auto Accessories Co. and Johnson Controls.
According to environmental authorities, the two plants were emitting dust and smoke containing lead into the area.
U.S.-based Johnson Controls, which manufactures batteries, denied the accusation.
"We are aware of the questions that have been raised by concerned local citizens about their potential exposure to lead in the area," Yu Dan, a representative of Johnson Controls Shanghai, told CNN. "However, we have no reason to believe we are the source of the issue."
Johnson Controls said that its lead emissions in Shanghai are 1/7th the Chinese national standard, and that their plant employees are regularly tested to ensure blood levels are sufficiently low. The amount of lead emitted through waste water is 1/10 the Chinese national standard, the company said.
The plant belonging to Xinmingyuan Auto Accessories Co. was found to be using lead in its production without approval, the environmental bureau said.
A spokesman for that company said that its products containing lead take up only a small portion of their work.
"Products containing lead were taken off the production line on the day of the inspection," he said. "The company is only slightly involved in the lead issue."
In March of this year, 332 people, including 99 children tested positive for lead poisoning in Zhejiang province in eastern China. Local government suspended a local battery factory responsible for the poisoning.
CNN's Haolan Hong contributed to this report.