Peter Roeder, an animal health expert from the U.N. Food and Agriculture Organization in Rome, said tests so far had been negative for the virus, but antibodies were found in some specimens taken from chickens and ducks.

It's unclear, however, whether they were infected at the time the family members fell ill. They could have been sickened much earlier or developed antibodies after vaccination, he said, adding that no immunization records were available.

Dead poultry was also found in an area outside the village, but test results for those birds have not yet come back, said Roeder, who has worked closely with Indonesia to strengthen poultry surveillance and response to bird flu outbreaks.

Bjorge said the woman first believed to be infected worked as a vegetable vendor in a market where live poultry was sold.

Experts are trying to determine if that's where she became infected. The woman, who died May 4, was never tested for the H5N1 virus, but WHO considers her part of the family cluster. The woman's 25-year-old brother is the only family member still living after being infected.

"All confirmed cases in the cluster can be directly linked to close and prolonged exposure to a patient during a phase of severe illness," the WHO said in a statement on its Web site.

Bjorge said some samples have been taken from villagers, but that local authorities have resisted working with outside health experts. WHO has enlisted local villagers to help monitor the village for anyone experiencing flu-like symptoms.

If anyone is found to have even mild symptoms, they will be quarantined and given the anti-bird flu drug Tamiflu, he said.