China said Sunday it can't rule out bird flu in the death of a 12-year-old girl last month and has called on the World Health Organization to help with diagnosis. Three people living in central China's Hunan province came down with pneumonia last month following an outbreak of the deadly H5N1 bird flu among local poultry, the official Xinhua News Agency said. Of those, a 12-year-old girl died. Her nine-year-old brother and a 36-year-old school teacher recovered from the illness. Chinese officials initially said that the girl and her brother had tested negative for the virus. But on Sunday, Xinhua reported that experts "cannot rule out the possibility of human transmission of H5N1 bird flu. The specific cause needs further laboratory tests." Xinhua also said that China has asked the World Health Organization for help in testing the blood and throat swabs from the three victims.