Health officials in China fear a man who recently died may have been the country's latest victim of bird flu.
China has been put on its guard by warnings from officials
The 32-year-old man died earlier this week in the southern city of Guangzhou, just across the border from Hong Kong.
Meanwhile Indonesia said it believed a three-year-old boy who died this week may have succumbed to bird flu.
Local tests suggested the presence of the H5N1 strain and have been sent abroad for confirmation. Results from local tests are usually valid.
If confirmed, the boy would be Indonesia's 21st bird flu death.
Hong Kong concerns
If the death in China is found to be H5N1, it would be that country's ninth such fatality.
Hong Kong is watching closely. The territory has not been affected by the latest outbreak but it was where H5N1 first appeared and jumped to humans.
"Although there is no case in Hong Kong, we are mindful of the large volume of population flow between Guangdong and Hong Kong," a government statement for the territory said.
H5N1 first appeared in Hong Kong in 1997, when it killed six people.
The territory slaughtered its entire poultry flock of about 1.5 million birds.
H5N1 has killed more than 90 people, mostly in East Asia, since it re-emerged in late 2003.
It can be caught by humans who handle infected birds, but is not yet known to have passed from one person to another.
Scientists have warned that if the virus mutates, it could create a pandemic that could kill millions of people.
Last week China said it feared it could suffer a "massive" outbreak of bird flu this spring, if wild birds returning from their winter migration infect farm poultry.