New Zealand has assembled a six-strong team in Tonga to work on a Royal Commission of inquiry into the sinking of the ferry, Princess Ashika.
As many as 95 people died when the vessel went down last week.
The Transport Accident Investigation Commission team includes two master mariners and an engineer.
TAIC says initial contacts are being made and the team is familiarising itself with the situation.
It says work on its investigation won't start until the Royal Commission is fully up and running.
TAIC was called in because the Attorney General of Tonga says his nation doesn't have the technical expertise and resources to conduct such a big inquiry.