The Department of Conservation says the loss of one its volunteers on Raoul Island appears to be a freak accident.
Mihai Marcus-Nagy from Romania is thought to have been swept off the rocks while taking sea temperature readings on the coast of the remote island.
An extensive search for the 33-year-old began on Monday, but was called off on Wednesday after DoC said he had been missing too long to have survived.
Raoul Island is part of the Kermadec group, 1000km north-east of the New Zealand mainland and the most remote conservation area managed by the department.
DoC chief executive Al Morrison told Radio New Zealand's Summer Report on Thursday all work on the island has an element of risk, but he defended DoC's procedures.
"We do feel we've got best practice. We've got very good training and we would only take very experienced staff there, and they're well led.
"Having said that, obviously, there will be a Department of Labour investigation into this and we're very anxious just to learn any lessons from it and to apply them."
Mr Morrison says what happened may never be known but it appears to be a freak accident.
DoC's area manager for the Kermadecs, Tim Brandenburg, says Mr Muncus-Nagy was a conservation worker who came to New Zealand because of its reputation as a world leader in the field.
"His enthusiasm, his skills leapt off the page at us and we snapped him up. He fitted into the team incredibly well.
"He was passionate about conservation, he got on with everybody, he was popular - which just makes it so sad."
Al Morrison says Mr Marcus-Nagy's wife is distraught and DoC is looking at plans to bring her to New Zealand so she can visit Raoul Island.