Nearly 100 children in Hunan province in Central China were found to have suffered from the second lead poisoning case in the country within a month, and local authorities said 600 children altogether are being tested.

An unlicensed manganese smelter unleashed the toxic substance, said environmental authorities in Wugang county in the west of Hunan.

Police have detained two owners of the Jinglian Manganese Smelting Factory, which was built last August and went into operation earlier this year.