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".
Currently, the alert level is at three, indicating a "minor volcanic eruption".
Thirty-four people were rescued, and most of them are still receiving treatment in hospital. Doctors said some of their burns are so severe they may not survive.
Police said they were "unsure" what state the bodies that remained on the island were in, saying they were probably "covered in ash".
The tourist attraction remains too dangerous to access, but reconnaissance flights conducted earlier on Tuesday saw no survivors.
Ms Ardern said there were no signs of life on the island and that the focus was now "on recovery".
"To those who have lost or are missing family and friends, we share in your unfathomable grief in this moment at time and in your sorrow," she said.
