FIVE suspected Vietnamese robbers were given a new engine for their boat and escorted out of Hong Kong waters. Hours later, one of the five was arrested in Castle Peak, and a few days later a second suspect was detained in Tin Shui Wai. The Security Branch is understood to have ordered not only that the Vietnamese be given the replacement engine, but also that the charges against them be dropped. Officials are not keen for Vietnamese to be given prison sentences that would extend beyond 1997. China has repeatedly said it opposes any Vietnamese being left in the territory when it takes over sovereignty. Police sources said the men were intercepted in a Chinese-made speedboat near Cheung Chau on August 10 and told police they were bound for Japan to seek asylum. But their vessel contained only a hacksaw, an iron bar, a knife and a set of pliers, leading police to believe they were involved in the many burglaries being carried out on the outlying islands by Vietnamese illegal immigrants. They were arrested and charged with the possession of instruments for an illegal purpose. But the group was released on September 4 after police 'received instructions' to drop the charges because of insufficient evidence. The five were unable to leave Hong Kong because of problems with their boat's engine. Under the Government's so-called Millport Policy, Vietnamese seeking asylum elsewhere are entitled to food, water and fuel before being escorted out of Hong Kong waters. 'They were taken out of Hong Kong waters and all they did was head back into Hong Kong,' a police officer said. 'One of these guys was picked up within 51/2 hours of the boat being escorted out.' The Security Branch declined to comment on the case. The South China Morning Post reported in July that Vietnamese operating in small boats were behind a campaign of 'plundering and pillaging' of homes and businesses on outlying islands. The raiders were believed to be using sampans and small boats and operating from a mother ship anchored in Chinese waters. Their raids have frustrated police who must release the suspects under the Millport Policy if they do not catch the Vietnamese in the act of committing crimes. One man involved in the raids is known to be a former detainee of Hong Kong's Vietnamese detention centres who was repatriated after failing to gain refugee status.