SHANGHAI - Three local companies have been held responsible for a lead poisoning incident involving 49 children in Shanghai, according to a report issued by the municipal government Saturday.

Of the 1,306 children living in the Kangqiao area of Pudong district who had their blood tested in late 2011, 49 children, mainly between the ages of one and three, were found to have elevated blood lead levels, the report said.

An investigation conducted by environmental and health authorities showed that the children became ill after being exposed to airborne lead, the report said.

The report cited a battery manufacturer, auto parts maker and a recycling company as being connected to the elevated lead levels.

The report said Shanghai Johnson Controls International Battery Co., Ltd. discharged excess airborne lead as it expanded production without governmental permits, identifying the company as the major source of lead contamination in the area.

Shanghai Xinmingyuan Automobile Parts Co., Ltd. was found to have used lead on its production lines without authorization.

The investigation also found excessive levels of lead and zinc in the soil near a plant that recycles used goods and materials.

All three businesses have been shut down for the time being.

The municipal government is working to formulate pollution emission standards for battery plants to prevent similar incidents from happening in the future.

An initial report on the poisoning surfaced in early September, when several children were found to have excessive levels of lead in their blood during physical checkups conducted before the beginning of the new kindergarten and primary school semesters.

Three of the sickened children are still hospitalized, the report said, noting that their condition has gradually improved.