Fears of a new bird flu outbreak intensified yesterday with the discovery of infected chickens at four wet markets in urban areas, a day after the virus killed chickens at a Mui Wo market. Tests on 24 chickens at a total of nine stalls in the markets in Wan Chai, Tsuen Wan and Wong Tai Sin showed they had the H5 flu virus. Further tests were being carried out last night to establish if it is the H5N1 sub-strain which jumped the species barrier and killed six people in the bird flu outbreak in 1997. Some 1,200 chickens for sale at the nine stalls were slaughtered. A Food and Environmental Hygiene Department (FEHD) spokesman said the nine stalls were ordered closed for cleaning as authorities try to trace the source of the outbreak. It comes barely a week after ducks, geese and swans died from an H5 flu strain at Penfold Park in Sha Tin. On Wednesday, the H5 virus killed 22 chickens at a market stall in Mui Wo, Lantau Island. The government last night appealed to the public not to panic over the latest cases, saying there was no sign of a large-scale attack. The FEHD spokesman called yesterday's discoveries 'normal'. But legislator Lo Wing-lok, who is an infectious diseases expert, said: 'I am concerned about the virus spreading.' He said now was usually the peak season for flu and with the winter solstice coming, there would be a huge demand for live chickens. Dr Lo said he was told that on Wednesday alone, 130,000 live chickens were imported from the mainland. He said high import volumes could sometimes result in reduced quality controls. Inspectors found the dead chickens yesterday at the Yeung Uk Road and Heung Che Street markets in Tsuen Wan, Tai Sing Street Market in Wong Tai Sin and Bowrington Road Market in Wan Chai. The markets contain 57 poultry stalls in all. Dr Lo said all the chickens on these stalls should have been slaughtered as well. 'The virus can kill birds in a matter of hours,' he said.