Ministry spokesman Wu Heping said at a press conference on Tuesday that police had detained 30 people in a large-scale rescue operation of slave laborers in small brick kilns and mines in Shanxi.

"At present, the police are searching for more than 20 suspects who are believed to be still on the run," Wu said.

Five of those arrested had so far been charged, including 42-year-old Heng Tinghan who was arrested in connection with the death of one worker and the injuring of 20 others.

The ministry dispatched criminal investigation experts to Shanxi Province last week to guide and monitor the investigation, said Wu.

Police have arrested 168 people accused of operating workers in appalling conditions at small brick kilns and mines in Shanxi and neighboring Henan Province.

By Saturday, 315 people -- including 22 aged under 18 -- had been freed after police raided more than 3,700 small brick kilns and collieries in the coal-rich Shanxi Province, many of which were unlicensed.

Meanwhile, police in Henan had freed 217 forced laborers, including 29 juveniles and 10 mentally handicapped people, said Wu.

The slave labor scandal hit the headlines after a "call-for-help" letter was posted on the internet earlier this month by more than 400 parents in Henan who believed their missing children had been sold to the small brick kilns as slave workers.