From Radio Free Asia (link):
Groups of parents throughout China have formed a last-ditch alliance in the hope of recovering their missing children, who are believed to have been kidnapped and sold in a booming adoption, bridal and sex trade in human beings.
While the phenomenon occurs right across China, recent interviews with migrant workers in the southern economic boomtown of Dongguan have revealed a virtual black hole from which dozens of children have never emerged, with some estimates saying that as many as 400 have “disappeared” in the area.
“When he was at the Dongguan public security bureau, we asked him if he knew how many children were missing in Dongguan. He said one official told him that more than 400 children are missing,” said the couple’s representative, identified by his surname Zheng.