Two ducks and a goose infected with H5 bird flu have been found dead on Lantau Island, prompting an expert to warn that Hong Kong could be hit by an outbreak of the deadly H5N1 strain of the virus at any time. The bodies of the goose and one of the ducks were found on a beach at Sha Lo Wan near the airport on Thursday. Officers from the Agriculture, Fisheries and Conservation Department collected the body of another duck from the same spot yesterday. Preliminary tests on all the birds showed they had H5 bird flu. More tests are needed to determine whether they died from the potentially deadly H5N1 strain. University of Hong Kong microbiologist Ho Pak-leung said the find showed the city was at growing risk from the H5N1 virus. Dr Ho said this was the third time in a year that bird flu had been detected in the city. 'This shows that the virus can spread to the city at any time,' he said. The government must step up efforts to enforce its ban on the keeping of backyard poultry and review its efforts to combat the cross-border smuggling of poultry, he said. There are no poultry farms within 3km of Sha Lo Wan and a sweep of surrounding villages found no evidence of poultry being kept by villagers. Officers from the department are investigating whether the birds were dumped on the beach or washed ashore. A spokesman said the department was very concerned at the discovery and had increased inspections of the area. It urged the public to report any sick or dead poultry or wild birds promptly. Health authorities have been working at a 'serious response level' since December 9, when bird flu killed chickens at a Yuen Long farm. Thousands of birds were culled at the farm, which remains closed. H5N1 first jumped the species barrier to infect humans in the city in 1997, killing six people, and has since killed more than 250 worldwide.