Police cordoned off a street in Mong Kok for six hours yesterday to reconstruct an acid attack that injured 30 shoppers, while detectives revealed they had narrowed their search to just a few suspects. They were among more than 20 people captured on surveillance cameras in the Foo Tai Building 30 minutes after Saturday's attack, according to a police source. The source said the attacker should be among these 20-odd people as police believed the two bottles of acid were tossed from the roof of the commercial building on to the pedestrian zone in Sai Yeung Choi Street South. 'They included men and women. Footage showed that they were ... carrying either a bag or a backpack while leaving the building.' Over the past few days, plainclothes officers with images of the 20-odd people have returned to the scene and talked to security guards and tenants to eliminate suspects one by one. The source said their search had been narrowed down to several people. But police could not yet be certain whether one of them had indeed carried out the attack. Senior Superintendent Edward Leung Ka-ming, head of the Kowloon West crime unit, said officers were still checking footage from surveillance cameras seized at the scene. At about 3am yesterday, officers from the police tactical unit cordoned off a section of Sai Yeung Choi Street between Shantung and Dundas streets for the reconstruction. Seventeen plastic bottles of liquid were thrown from the roof of two buildings - the Foo Tai Building and the Pakpolee Commercial Centre. Three more were tossed from a hydraulic platform at a height of six storeys outside the Foo Tai Building. Nine of the bottles contained an acid drain solvent similar to the one used in Saturday's attack. Some shops were covered in plastic sheets to avoid damage. A team of government chemists, firemen and officers from the Identification Bureau helped in the reconstruction. 'Government chemists will carry out a detailed analysis of data and comparison with the evidence seized at the crime scene on the day of the attack,' Mr Leung said. Mr Leung said police had to wait for the results from government chemists before they could find out from which building and which floor the bottles of acid were thrown. The exercise ended at about 8am before hygiene workers were called in to clean the road. The road was re-opened before 9am. Saturday's case was identical to an attack in December in which 46 people were injured. The two sites are in the same street, about 150 metres apart. Police suspect the cases are linked because the bottles and drain solvent appeared to be the same. Officers from Kowloon West crime unit have consolidated investigations into the two cases and tripled the reward to HK$300,000 for information leading to the arrest of the offender or offenders. Anyone with information can call a 24-hour hotline on 2761 2401.