A sex workers' concern group demanded police apologise for holding 40 mainland women suspected of prostitution in a cramped cage in public view, and claimed the women had been assaulted by police while in custody. About 30 protesters led by Zi Teng gathered at the Tsim Sha Tsui police station yesterday chanting slogans accusing the police of humiliating the women and forcing some to sign confessions. The women were arrested on Monday and kept in what police term a temporary holding area while officers checked their identities and took statements. The cage, about 14 square metres, is sandwiched between the police station building and its car park. The protesters brought a paper cage they filled with written accusations concerning the treatment of the suspects. Senior Inspector Li Yuen-mei accepted a petition from the protesters but not the paper cage. 'Some mainland women who were locked up in the cage told us they were forced to sign confessions in return for early release after which they were sent back to the mainland,' the group's spokeswoman, Elaine Lam Yee-ling, said. If they refused to sign they would be kept in prison while awaiting their trials as they had no address in Hong Kong and could not be released on bail, she said. She also had been told some officers had slapped the faces of some women and knocked their heads against walls. The police did not respond to this accusation. The immigration department said all mainland women arrested on Monday had been repatriated.