The Royal Commission of Inquiry into Tonga's ferry disaster says it wants it understood that no evidence it gathers will be given to any other authority.
The Commission is investigating the sinking last month of the Princess Ashika, in which more than 70 people are presumed to have drowned.
A spokesperson for the investigation team from the New Zealand Transport Accident Investigaton Commission that's assisting the Royal Commission of Inquiry, Peter Northcote, says the evidence it receives will have immunity.
"The reason for this is that these investigations are about safety first, finding out what happened, what the circumstances were, how they came about, and what can be done to ensure that a similar event doesn't happen in the future. Other authorities have responsibility for any liability issues that might be involved."
Peter Northcote says if the Commission comes across something that could point to criminal responsibility it will alert other authorities, but it will not provide them with evidence.
He says the Tonga Police are doing a very thorough investigation.