Egg smuggling may not explain the bird flu outbreak, as most dead chickens found in a Yuen Long farm were probably not hatched from infected eggs, an official says. Trade sources claimed last week that fertilised eggs with infected embryos smuggled from the mainland could be spreading the disease. But Thomas Sit Hon-chung, the Agriculture, Fisheries and Conservation Department assistant director for inspection and quarantine, said most of the dead chickens were too mature. 'If smuggled eggs caused the outbreak, sick chicks should have been found,' he told a Commercial Radio programme yesterday. Nonetheless, Dr Sit said the department was closely monitoring the numbers and shipments of eggs. He said the department had collected samples for examination but the exact cause of the outbreak was still unknown. Leung Ting-hung, head of surveillance and epidemiology at the Centre for Health Protection, said laboratories at the University of Hong Kong and the agricultural department were analysing the samples. Findings were expected in a week. The outbreak last week at a farm owned by Wong Yee-chuen, secretary of the New Territories Chicken Breeders Association, killed 200 chickens. Health workers had to cull tens of thousands of chickens.