Two people from one family, who died earlier this week in West Java province, have been tested positive to bird flu virus by a local lab, the Indonesian Health Ministry said in Jakarta Thursday.
"They are brother and sister, both are positively infected," Director of Health and Environmental Health of the Ministry I Nyoman Kandun Kandun told Xinhua.
However, he could not confirm whether the two had contact with fowls.
Their blood samples have been sent to the World Health Organization affiliated laboratory for bird flu test in Hong Kong, he said.
The death of the two came after the biggest bird flu cluster death in North Sumatra province earlier this month.
Indonesia is probing into possible human-to-human transmission.
Experts fear that the virus could mutate to a certain form that can easily transmit from human to human, which can kill millions of people.
The WHO has confirmed 32 people have been killed by the highly pathogenic H5N1 virus in Indonesia.