The President of the Papua New Guinea province of Bougainville, Joseph Kabui, says it may take up to two years before his administration is able to establish the cause of death of rebel leader Francis Ona.
Mr Ona died suddenly two weeks ago, reportedly from malaria and possibly typhoid, but Mr Kabui says rumours are circulating that there was foul play involved.
Mr Ona was buried two weeks ago without an autopsy, even though his family wanted the body flown to Buka for the procedure.
Mr Kabui says given the lack of access for his officials to the No Go Zone where Mr Ona is buried, it could be up to two years before they get an opportunity to determine the cause of death.
"I think we are prepared to let things go on for that long, until things can be cleared and then we can get to the bottom, establishing whether the strong rumours flying around do have some substance."
