CORRECTIONAL Services Department (CSD) officials yesterday examined seven surveillance tapes of the violent blockade at the High Island detention centre but failed to find enough evidence to take action against six suspected ringleaders. Video recorders, set up at lookout posts and on top of a fire engine hydraulic ladder before the stormy repatriation exercise on Thursday, did not add weight to information received from Vietnamese at the centre. The failure to gain evidence follows widespread anger among police and CSD officers over the Government's decision not to charge four Vietnamese accused of assault in a similar exercise at Whitehead in May. Corrective Services Officers Association (junior section) chairman Fung Kin-hung said last night he believed senior officials were following a Government practice not to charge Vietnamese. 'I just can't believe it. I watched the footage on television - there seems to be plenty of evidence,' he said. The six suspects, believed to be part of a group of 30 resistance leaders, were isolated and questioned for about two hours on Thursday after security forces broke the blockade at the north camp by using a Saxon armoured personnel carrier. CSD officers allowed the suspects to rejoin the camp after the interviews did not establish sufficient evidence that they had orchestrated the lockout tactic. The tactic disrupted the repatriation of 163 Vietnamese and resulted in 14 security officers being injured. CSD Assistant Commissioner (Vietnamese) Bonnie Wong Yuk-man said charges would be laid if evidence was obtained.