"Black jails" run by security companies to intercept or confine "deviant petitioners" have not yet been swept out of the capital, according to Beijing police who said they recently dismantled one such jail in Changping district.

Wang Wenjie, a publicity official with the municipal public security bureau, told China Daily on Tuesday that police in Changping caught several suspects who were running the illegal detention house after a released petitioner gave them information.

Police also rescued several petitioners detained there, Wang said.

The police officer, however, did not reveal how many suspects were detained or if the black jail, which was located somewhere in Lingshang village, Beiqijia township of Changping, had been closed down.

"All I can say is that the black jail is one individual case," Wang said, indicating there is no other illegal detention house in the city.

The issue of black jails shocked the nation last year when media reported that a local government had paid security companies to intercept and lock up - normally by force - "deviant petitioners".

Under the law, people from all over the country with grievances against governments can come to the capital to present their case to the State Bureau for Letters and Calls.

In September, Beijing Municipal Public Security Bureau detained Zhang Jun, chairman of Anyuanding Security Service Company, and Zhang Jie, general manager of the company, for "illegally detaining people and illegal business operations".

The company started business in 2004. In 2008 it began to help liaison officers from local governments in Beijing who wanted to stop people from petitioning, according to the police investigation.

China's latest version of Regulations on Letters and Visits does not define "deviant petitioners", but states if the letter-writer or visitor violates the laws or administrative regulations on processions and demonstrations, the public security body shall take necessary measures and impose an administrative penalty.

The Beijing News reported on Tuesday that information from a petitioner surnamed Zhou, who was released from the "black jail" in early July, led to the police operation.

Zhou, from Yancheng city, in East China's Jiangsu province, said as soon as she walked out of a government office in Beijing on July 4, several men blocked her way and dragged her into a minivan.

The men confiscated Zhou's mobile phone and drove her for an hour to a courtyard of three houses measuring about 60 square meters, the report said.

"There was no bed in my room. Elderly people and babies were sitting or lying on the ground," Zhou was quoted as saying. "It was hot, humid and airless."

She added that about 50 people from different places were detained in the courtyard with her. The houses were heavily guarded and it was "difficult to run away".

Zhou was released four days later for good behavior, but she said some people had been held there for months.

In last year's Anyuanding case, police took most "deviant petitioners" in Beijing to Majialou reception and rescue center, from where the petitioners were taken away by hired security personnel to black jails or sent home.

An owner of a grocery store near the Majialou center, surnamed Li, told China Daily she saw many petitioners being treated roughly.

"I once saw a petitioner pushed down from a truck. He almost had his leg run over," Li said.

Yu Jianrong, a professor at the Chinese Academy of Social Sciences, said the black jail case in Changping will not be the last one in Beijing.

"There is a chain of interests behind the control of petitioners," Yu said.

"The security company wants to make money from it, and the local government needs help from outside to maintain stability and fulfill their obligations."

Yu said only when the "system of maintaining social stability changes can the issue of black jails be eliminated completely".