SHANGHAI, Jun 21 -- HUNDREDS of fathers from Henan Province posted another letter to call for rescue efforts to continue for their missing children, who they believe are still working at illegal brick kilns as slave laborers or have been moved to secret locations by kiln owners, a Hunan-based newspaper reported today.

The 400 fathers have saved more than 100 children from "black kilns," but most are neither their children nor Henan natives, Xiaoxiang Morning Post reported.

Their previous calls have led to the rescue of more than 370 slave workers in Shanxi.

"Only two Zhengzhou families in Henan were told that their children have been rescued in the campaign," the letter said.

Some rescued children said they were lured to Shanxi with some of the fathers missing kids, and some worked together for a month while others were separated after arriving in Shanxi.

"Henan Television Station can offer videotapes as evidence," the fathers said in the letter.

A Shanxi public security official said on Tuesday that some kiln owners have transferred the slave workers in advance to avoid checks, the report said.

In a rescue operation late last month, Shanxi police freed 31 slave workers at a kiln in Hongdong County. They were too late to help one worker, who had been beaten to death, officers said.

All those involved in the case have been detained. Wang Dongji, the father of kiln owner Wang Bingbing, was sacked as Party chief of Caosheng Village, said Zhang Mingqi, a senior official in the All China Federation of Trade Unions, at a news conference on Monday in Beijing.

Shanxi police have checked 93 kilns in Hongdong County and only two possessed the proper licenses.

"Hongdong's slave-kiln case is only the tip of the iceberg. There are more than 1,000 lives waiting to be rescued," the letter said.

Fu Zhengzhong, a reporter of Henan Television Station, said more than 1,000 parents have called them for help to find missing children.

"Each of the kilns that police investigated in Wanrong County, Shanxi, had more than 10 children working as slave laborers. There are many more kilns in the province that haven't been checked, so we estimate there are at least 1,000 children still slaving away in Shanxi kilns," Fu added.

The central government announced it will overhaul employment practices nationwide, mainly targeting small brick kilns and coal mines, in the wake of the ongoing slave-worker scandal.

Any business owners found to employ minors, illegally force laborers to work or maliciously injure them will be severely punished, according to a State Council meeting chaired by Premier Wen Jiabao yesterday.

On behalf of the provincial government, Shanxi Governor Yu Youjun made a self-criticism during the session.

The central government urged local governments across the country to learn a lesson from the scandal and ordered the Shanxi government to step up efforts to deal with the scandal and compensate victims.

The Supreme People's Procuratorate yesterday sent two prosecutors to join a local task force addressing the investigation of alleged negligence by Shanxi officials.