New Zealand Prime Minister Jacinda Ardern has said there are questions which “must be asked” after the volcanic eruption on White Island.
Five people are dead and eight are missing on the island – though police say they are also likely to have died.
Officers earlier announced that a criminal investigation would be opened, but later revised this, saying it was “too early” to say.
Some 47 people from around the world were on the island during the eruption.
“We know there will be bigger questions in relation to this event,” Ms Ardern said. “These questions must be asked and they must be answered.”
Three weeks ago, the threat level at the volcano had been raised from one to two (out of five), describing the situation as “moderate to heightened volcanic unrest”.
Since the eruption, experts are arguing whether the tours to the island were a disaster waiting to happen or still safe enough for visitors.
Yet while geological hazard monitoring group GeoNet last week warned White Island “may be entering a period where eruptive activity is more likely than normal”, it also said “the current level of activity does not pose a direct hazard to visitors”.