The World Health Organization is still waiting for China to hand over tissue samples from bird flu outbreaks in poultry.

WHO officials say getting information on China's 26 reported outbreaks in animals this year could help formulate effective vaccines and other prevention measures.

China has given no clear explanation of why it has not sent WHO the samples. Foreign Ministry spokesman Qin Gang told reporters Tuesday that China believes in international cooperation to deal with the threat of bird flu.

WHO's regional director for the Western Pacific, Shigeru Omi says that seeing the tissue samples would allow researchers to know what changes the virus is undergoing, which would be crucial to developing an effective vaccine to contain the spread of the disease.

Tuesday, Turkey and Romania announced new bird flu outbreaks.