The scientists were undertaking fieldwork for the Institute of Medical Research when they went missing off the coast of West New Britain.
Despite numerous searches, little trace of them has been found, although their boat was later thought to have washed up on the Sepik coast.
Police previously believed the scientists had been kidnapped, but have now closed the case.
The director of the Institute of Medical Research, William Pomat, said the coroner's report was also inconclusive
