A 30-year-old Lamma ambulanceman was killed yesterday when his vehicle overturned while taking a woman to the island's clinic. A resident said the new models which replaced Lamma's three small fire engines and the ambulance a year ago were top heavy and unstable. The 29-year-old patient, and two other crewmen, aged 34 and 52, remained in Queen Mary Hospital last night, along with a 53-year-old passer-by who injured his left arm trying to rescue the four. All were stable. The five victims were airlifted to the hospital after the accident, which happened at 7.30 am on a steep slope near Yung Shue Wan. The driver suffered extensive head, back and leg injuries and was certified dead on arrival. The ambulance, smaller than normal because of the narrow streets, was the only one on Lamma. Resident Liz Gower claimed the new two-wheel-drive fire engines and ambulance replaced four-wheel-drive models, and were known to be unstable. 'Every time they went downhill, they had to get people to jump out because they were tremendously top heavy,' she said. 'The firemen treated it all as a joke, until about a year ago when the driver of the fire engine had to jump out when it toppled. He was lucky he was quick, or else it would've landed on him.' A Fire Services Department spokesman said an internal investigation was under way, and he could not comment. Hong Kong Island traffic police were also investigating. Similar vehicles, made in the United States, were used on Cheung Chau and Peng Chau, a Fire Services Department spokesman said.