POLICE believe a serial rapist in Tuen Mun has murdered his latest victim. The half-naked body of the 50-year-old woman was found in a stairwell of a block on Yau Oi Estate yesterday morning and police are concerned there could be further attacks. The assistant district commander (crime), Detective Superintendent Raymond Pierce, said he had not ruled out the killer being the serial rapist responsible for five cases on Yau Oi and Tai Hing estates in the past six months. He said it was difficult to get a good description of the suspect because the victims were grabbed by the neck from behind. The previous victims were aged between 19 and 40. ''All we know is that the attacker is aged between 25 and 30 and tends to commit the offence in the lift lobby or inside the lift in public housing estates,'' he said. Police said the body of the latest victim, Ms Lee Hing, was found in the stairwell between the ninth and 10th floors of Oi Shun House at about 7 am yesterday by a man going downstairs. She was naked from the waist down, with the clothes on her upper body dishevelled. Her underwear and jeans were found nearby. Mr Pierce said it was possible that Ms Lee was followed into the lift by the rapist when she arrived home early yesterday after a mahjong game. She was on her way up to a third-floor flat where she lived with her husband and four adult children. Police have not yet recovered her handbag. A staff officer (crime), Detective Superintendent Patrick Pong Wai-lung, said the case had been classified as murder but police believed the victim had been raped as well. Mr Pong appealed for witnesses; anyone who might have information is urged to contact the police on 527 7177. Elected Tuen Mun District Board member Mrs Choi Cheung Yuet-lan(Cont'd from Page 1) called on the police to set up a special task force to hunt down the killer. A police source said it was difficult to pick up the pattern of a rapist because the number of rapes was comparatively low in Hongkong and it was rare to have a serial rape case in the territory. There were 116 cases of rape last year; the figures for 1991 and 1990 were 114 and 111 respectively. A computer information processing system has been on-line since mid-1991 to assist in complicated investigations and major disasters. The system, called the Major Incident Investigation and Disaster Support System, is similar to that used in the investigation of the bombing of a Pam Am jet over Lockerbie in Scotland. It is designed to aid investigations into complex crimes such as multiple murders or disasters. The computer's main search parameters are names, addresses and telephone numbers. Suspects also can be classified by tattoos, jewellery, or even aftershave used. The source said the computer was recently used in investigations into the Lan Kwai Fong disaster and a spate of armed jewellery shop robberies. Officers familiar with the system have warned that its effectiveness is heavily dependent on the quality of information put into it, saying that inputting police files would take some time.