China has arrested two labour bureau officials for their alleged links to slave labour in brick kilns, amid reports Friday that kiln bosses were hiding child labourers and charging ransoms for their release.

The pair are the first officials arrested in connection with the enslavement of hundreds of children and adults at brick factories where they were forced to work long hours in gruelling conditions without pay.

The head of the labour inspection team in Yongji district of Shanxi province has been charged with dereliction of duty, and one of his officers has been charged with abuse of power, the official Xinhua News Agency said Friday.

It said the two officials were responsible for abducting an underage labourer who had been released from a kiln and was being transported home. They then sent the boy to another kiln where he was again forced into slavery, it said.

The victim wasn't identified, but the Associated Press interviewed a father in Henan Province who said his missing 17-year-old experienced a similar situation.

Thorough probe ordered

The scandal that has brewed on the internet and in state media prompted an extraordinary self-criticism this week from Shanxi Governor Yu Youjun, making him the first high-ranking official to perform a potentially career-damaging act of contrition in relation to the case.

That came during a cabinet meeting on Wednesday presided over by Premier Wen Jiabao, who has built his public image on concern for the welfare of ordinary Chinese. Wen has ordered a thorough probe and punishment of kiln owners and officials who abetted their activities.

Since the scandal broke last month, more than 8,000 kilns and small coal mines in Shanxi and Henan provinces have been raided, with 591 workers freed, including 51 children, according to state media.

About 160 suspected kiln bosses have been detained in the two provinces, and at least one village-level Communist Party secretary expelled from the party after his son was found to be operating a kiln where 31 slaves were found labouring under extraordinarily cruel conditions.

Children kidnapped, lured

Workers, including small children, were kidnapped or lured with false promises of well-paying jobs by recruiters at train and bus stations. Sold on to kiln owners for $65, they were beaten, starved and forced to haul bricks for up to 20 hours per day for no pay.

Many of those rescued showed serious injuries from burns and beatings.

Investigations have been spearheaded largely by parents searching the mountains of southern Shanxi for missing sons. One group claiming to represent 400 fathers circulated an open letter online saying 1,000 children were being held and accusing officials of ignoring or obstructing their searches.

However, reports Friday said some parents had been contacted by their abducted sons who told them they would be released on payment of a ransom.

The official China Daily newspaper reported that a family surnamed Yuan said their son told them the kiln boss was demanding $4,600 for his release. It said other operators had been tipped off to raids and shifted their slave labourers to remote hiding places.