Researchers say respiratory bacteria and a mosquito-borne virus caused the death of dozens of children in Indonesia's Papua region last month.
The Papua Health Office announced in November that 41 children died in Nduga regency from an unidentified disease.
The Jakarta Post reports tests on samples taken from the victims showed that the respiratory bacteria, pneumococcus, and Japanese encephalitis were spreading in the area.
Health authorities sent teams of doctors, nurses and researchers to investigate the deaths of the children, who were mostly under the age of two.
The researchers say the Japanese encephalitis virus could be transferred from humans to animals or vice versa.
People have been urged to keep their neighbourhoods clean to prevent mosquitos from breeding.