More than 30 mainland overstayers have filed formal complaints detailing alleged abuse inside detention centres, in response to authorities' refusal to investigate the allegations without individuals stepping forward. However, many of the 176 overstayers who claimed they were mistreated while being held over a period of one or two days earlier this month are expected to shy away from making a formal complaint for fear of retribution. Patrick Tse Pak-chai, an overstayers' advocate, said many of the detainees refused to write letters of complaint because they did not want to jeopardise their chances of staying in Hong Kong. 'They're scared about what would happen to them if they're detained again and they're scared of being deported. They don't want this to affect their bid to stay here,' he said. Many of the detainees had stated in a survey and told reporters that they were intimidated and humiliated in the detention centres. They claimed guards forced them to undergo unnecessary strip searches and to do squatting exercises while naked. They said guards also pressured them to sign voluntary repatriation forms in the middle of the night. The complaints have been forwarded to the Immigration and Correctional Services departments which were responsible for detaining the mainlanders seeking the right of abode. The detainees had previously filed a group complaint but the departments said they could not investigate the matter without specific details from individuals. They pledged that any personal complaints would be checked thoroughly and kept confidential. But the mainlanders, their lawyer and human rights activists continued to insist on an independent inquiry, which they said was the only way to get to the truth.