HONG Kong drug addicts who go to Shenzhen to cure their addiction are locked up in crowded cells and treated like criminals, the Sunday Morning Post discovered on a visit to a detoxification centre in Bao An - a 40-minute drive from Lowu. Patients housed in poorly ventilated dormitories could be heard banging on a single, barred window and shouting to be let out. According to a member of staff at the centre, drug addicts were admitted both on a voluntary basis or after their arrest by police for possessing or taking drugs. Authorities say they are put in separate wards. However, inmates deny this and when the Sunday Morning Post was at the centre, addicts banged on the iron bars on the sole window of their ward and yelled: ''Let me out! . . . I've committed no crime, why put me here?'' There were up to 10 addicts in a 40-square-foot ward, which also contained a toilet. As there was only one window, the room was stuffy and stank. Beds were close together and the crowded conditions led to arguments and fights. Patients' daily exercise consists of a walk around the compound. They are also given a lesson in law and allowed some time in the library each week. ''It looks more like a prison than a treatment centre,'' said addict Yan Kaiying, 30, from Sichuan. ''I have taken drugs for more than a year. I tried to kick the habit a few times in a clinic closer to home, in Chongqing, but couldn't . . . one of my friends told me there was a clinic in Shenzhen which was good, so I came here. ''I flew to Shenzhen on March 13 and arrived at the treatment centre the next day. I came here voluntarily - I still have the plane ticket with me to prove it,'' she said. But a uniformed member of staff stopped Ms Yan from showing the ticket. ''They put me into a separate ward for the first few days and I received medical treatment,'' Ms Yan said. ''But since then I've been put in with other people.'' According to Ms Yan, the other women in the ward were triad members or prostitutes who had been arrested for taking drugs. They were locked up in the ward as punishment and as a way to help them kick their habit. ''They are so violent,'' Ms Yan said. ''They often beat me up . . . and take my things. They took my blanket when the weather was cold . . . they see me as an outsider.'' She believed the reason for putting her in the ward was related to the fact that she had run out of money. ''I've only got 700 yuan [HK$620] with me. But the medical fees here are 2,000 yuan, so they won't let me stay in a separate ward.'' The Sunday Morning Post later confirmed with one of the centre's ''instructors'' that Ms Yan had entered the centre voluntarily. ''But she flouted the regulations, so we put her in the locked ward with the others,'' he said. Meanwhile, registration records showed that at least five Hong Kong men had stayed at the centre in the past three months. All had gone there voluntarily. On our visit only a man named Mak was still there, but he was sleeping off an injection in a separate ward. A spokesman for Hong Kong's Society for the Aid and Rehabilitation of Drug Addicts (SARDA), William Tang, said if drug addicts had attempted to break their habit on several occasions and had failed it was not surprising they sought help across the border. ''Shenzhen is so close it's no wonder they would try. I've heard of cases unde r SARDA's supervision going to Shenzhen before,'' he said. ''But I must caution them to get as much information about these treatment centres before they decide to go.'' Hong Kong drug addicts also go to Shenzhen to feed their addiction. ''It is common to see teenagers from Tuen Mun come here to buy drugs,'' said one 20-year-old patient in a new Shenzhen drug clinic. ''I have a neighbour who migrated to Hong Kong two years ago. He often returns to take drugs with us. Sometimes he brings along his Tuen Mun friends too,'' he said. ''We provide them with No 4 heroin, and the Hong Kong teenagers provide us with soft drugs.''