To date 331 people, including nine children, were freed in Shanxi, bringing the total number of slave workers rescued in China to 548, including 217 freed in the neighboring Henan Province.

Shanxi has mobilized more than 14,000 police officers to raid more than 2,500 brick kilns, coal and iron mines across the province, according to Du Yulin, director with the provincial public security bureau.

The local government is contacting the families and the hometowns of the victims.

Twenty-four suspects have been detained.

Du said authorities have been given a deadline of 10 days to investigate every brick kiln, coal mine, iron kiln and interview every worker personally.

Du asked local authorities to crack down on illegal kiln owners and other criminals with a firm hand and punish officials according to law.

If local officials fail to save all the people before the deadline, they will face chargers of dereliction of duty, Du warned.

Shanxi launched a crackdown on Friday cracking on illegal workplaces. As of July 15, enterprises must have legal business licenses and migrant workers must register at public security bureaus, said Jin Shanzhong, deputy governor of Shanxi.

Employers must provide necessary working and living facilities for their employees and pay salaries on time. No beatings, overtime work, or child workers are allowed, he said.

Wang Dongji, Party branch secretary of Caosheng Village, is being investigated after his son was found to be an owner of the illegal brick kiln who forced 32 people to work under extremely cruel conditions.

Other county-level officials involved in the case are also being investigated.

Wang Bingbing, the kiln owner, and three taskmasters have been detained. Police are hunting for three other suspects in five provinces.

Police have rescued 31 people from slavery at the kiln. One worker was allegedly beaten to death last November.

China's central government will send a team of investigators to look into the use of "slave labor" at illegal brick kilns in central China, which has raised great concerns among the public.

The Ministry of Labor and Social Security (MLSS), which will head the team, said preliminary investigations show the incident may involve abducted and forced labor.

"The team will find out the truth as soon as possible, and we will go all out to rescue the workers who had been forced to work as slaves in the brick kilns," said Sun Baoshu, deputy minister of MLSS, on Friday.

"The criminal offenders will be dealt with to safeguard the legal interests of the workers," Sun said.