Police were last night hunting for a sex attacker who grabbed a 12-year-old girl in the street and dragged her into a public housing block in Chai Wan. The girl put up a struggle and managed to run off after being dragged into a lift, then taken to the rear staircase of a building in Siu Sai Wan Estate. Police said the attack could have been stopped if security guards were monitoring the building's surveillance cameras. The Form One student, who lives in the estate, was on her way to school at about 7.30am when she was snatched shortly after she left Sui Keung House, police said. 'The attacker grabbed the girl from behind and covered her mouth with his hand to stop her shouting,' a police source said. 'She was dragged for about 50 to 60 metres into a neighbouring block [Sui Lok House] through a side entrance and was taken into a lift. 'The girl was dragged out of the lift on an unknown floor and taken to the rear staircase where she put up a struggle and managed to run off.' The girl ran downstairs and called her mother, who dialed 999 to report the attack to police. The girl was unhurt but taken to Eastern Hospital for a check-up. Police said no weapon had been used. Officers mounted a search, but no one was arrested. Police said the attacker was about 30 years old. Last night, investigators were checking CCTV footage in an attempt to identify the man. An investigator said it was possible the man was a resident of the estate because he knew the password to gain entry into Sui Lok House. Police suspect elderly people doing morning exercises might have witnessed the attack and planned to question them. Last November, a taxi driver was arrested after he attacked a 16-year-old girl in Chai Wan. The driver hit her over the head with a hammer and tried to force her into the boot of his taxi.