A foreign-owned battery plant that was ordered to halt production after children living nearby were diagnosed with lead poisoning has denied emitting excessive levels of the heavy metal.

Gu Xinyu, a 1-year-old girl diagnosed as having excessive amounts of lead in her blood, receives treatment at a hospital in Shanghai on Sept 16. The cause is under investigation. [China Daily]

Six factories citywide were given temporary closure notices by the city government last Friday, including one in eastern Shanghai's Pudong New Area operated by Johnson Controls, a leading producer of storage batteries based in the United States.

The move followed a round of inspections prompted by reports that 25 youngsters in Kangqiao town were found to have excessive levels of lead in their blood.

Although authorities say some plants were targeted due to breaches in emissions standards, Johnson Controls - one of two factories on the list located close to Kangqiao - issued a statement saying it was included only because it has reached its lead production quota for the year.

The company also said it is conducting its own investigation to ascertain the source of the lead pollution.

"Recent media coverage about the suspension may have misled people into believing we produced excessive lead emissions, while we have actually halted production because we have exhausted the quota," said a company insider on Monday who did not want to be identified discussing the issue before the investigation is finalized.

"Not only have we set very strict standards for lead emissions, we also give regular medical checks to our workers," she said. "We also spend more than 3,000 yuan ($470) on health protection for each worker every month. Few of them have been found with excessive levels of lead in their blood."

Company officials met to discuss the suspension on Monday, she added, "as it has to do with the future of the 400 employees at the plant".

According to the Ministry of Health, a lead production plant needs to be 500 meters from the closest residential area. Johnson Controls' plant is 700 meters from the Kangqiao community.

China Daily was unable to obtain information on when the Shanghai plant reached its lead quota in previous years or whether it ceased production at that time.

Wei Huajun, director of pollution prevention for Shanghai Environmental Protection Bureau, said that Johnson Controls' plant was found to be producing excessive lead emissions in June, although he explained that was not the reason behind Friday's closure.

"We immediately asked the plant to rectify its production procedures (in June) and they did make some changes in response," he said. "They halted production recently because they reached their lead quota for this year."

Xinming Auto Accessories, which sits alongside Johnson Controls on the Pudong Kangqiao Industrial Zone, also received the government's halt order on Friday. This, Wei said, was because it has been using lead in its production illegally.

"This company did not obtain a permit from the bureau to use lead," he added.

A total of 12 children had to be admitted to Xinhua Hospital for treatment last week. As of Monday, six had been discharged.

"The lead levels of six of the children were reduced by 30 to 50 percent," said doctor Yan Chonghuai. "They will continue to take nutrition pills until a second medical check in a month."

He explained that summer is a peak time for lead poisoning and said cases can be prevented by people washing their hands frequently and thoroughly before meals.

"Children are more vulnerable to the impact of lead," he added. "A child will be poisoned if he or she has 100 micrograms of lead in their blood, while for adults it's 400 micrograms. Children can suffer from mental trauma or anemia."