China said Sunday that the possibility of human infection of bird flu in the three reported pneumonia cases in Hunan Province, including one death, could not be ruled out, a Ministry of Health spokesman said.

    The spokesman said the ministry had invited the World Health Organization experts to make a joint investigation and to find out the cause for the death. 
 
    Three people living in central China´s Hunan province came down with pneumonia from unknown causes last month following an outbreak of the H5N1 strain among local poultry. One of them, a 12-year-old girl, died. Her 9-year-old brother and a 36-year-old middle school teacher recovered.

    Since all of them were from a bird flu outbreak area and suffered from unknown kinds of pneumonia, the spokesman said the human inflection of bird flu could not be ruled out, and further laboratory tests will have to be carried out.

    Such tests are now being conducted by relevant laboratories under the China Center for Disease Control, the spokesman said. Since the causes could not be determined in a short time, China has invited WHO experts to work with Chinese experts to find the cause.

    Earlier reports said the girl and her brother had tested negative for the bird flu virus.

    There have been four outbreaks of the bird flu among poultry in China in the past several weeks, respectively in Inner Mongolia, Anhui, Hunan and Liaoning.

    Since late 2003, the H5N1 strain of bird flu has ravaged poultry stocks and jumped from birds to humans. Most of the human deaths, all in Southeast Asian countries, have been linked to close contact with infected birds. But experts fear the virus could mutate into a form easily passed among humans and possibly spark a worldwide pandemic.

    China has pledged it will be more open about reporting on bird flu.