More than 200 people, including 29 children, have been rescued after working as "slaves" in brick kilns in central China, state media reports.
Some 31 "slaves" were rescued at a brickworks last week
Tens of thousands of police moved in on the kilns in Henan province, arresting 120 people, Xinhua news agency said.
They acted after media reports claimed that children were being forced to work in kilns in neighbouring Shanxi province, Xinhua said.
Photos of distraught parents were also published.
Xinhua said that, following the reports of child labour, some 35,000 police were despatched to the 7,500 kilns in Henan.
They reportedly rescued 217 people, including 29 children.
Xinhua said the victims had been "enticed or sent by human traffickers to the kilns", where they were "beaten, starved and forced to work long hours without payment".
Henan's police governor Qin Yuhai vowed to "do everything we can to fight human trafficking and rescue those held captive".
Dirty and disorientated
There have been similar cases in a neighbouring province which received national media coverage after parents of the children launched an online campaign to find them.
On Wednesday, 400 men from Henan made an online appeal for help in their bid to rescue their children from brickworks hidden deep in the mountains of Shanxi.
They said they had "risked their lives" to rescue about 40, but believed at least 1,000 children had been kidnapped for sale to traffickers.
"We were shocked by what we saw," they were quoted by Chinese media as saying.
"Some children had been isolated from the outside world for seven years, and some were beaten and maimed because they tried to escape, and the backs of some were burnt by supervisors with burning red bricks."
Last week, 31 disorientated workers were rescued from a brickwork factory in Shaanxi.
They were reported to have been duped into working at the factory, and faced a harsh regime in which they worked unpaid for 20 hours a day with only bread and water in return.
Police said that when they raided the works they discovered foul-smelling workers, who had been wearing the same clothes for a year.
Eight were reported to be so traumatised by their experiences that they were only able to remember their names.