In August 2009, media uncovered a jail for petitioners from Anhui Province in Beijing after a 21-year-old woman filed a rape charge against one of the guards.

In January 2011, media reported another case in Beijing imprisoning petitioners from the Guangxi Zhuang Autonomous Region. Both were then shut down by police.

Local governments in rural China often outsource the signing of demolition agreements, explained Du Jianxiong, a researcher of rural development at the Chinese Academy of Social Sciences in Beijing.

They do not necessarily know what organizations do to get demolition agreements signed. "Although the measures are mostly not government decisions or intentions, we cannot say that the local government has no responsibility," he said.

A few media reports had exposed a handful of black jails, said Zhu Xiaoding, a Beijing-based lawyer.

"The responsibility of eliminating black jails in China should not be borne by the media but local executors of the law," he said.