"The island is unstable... the physical environment is unsafe for us to return to the island. It is important that we consider the health and safety of those that will return to the island," National Operation Commander Deputy Commissioner John Tims told reporters on Monday night.
It is unknown what nationalities the dead are.
A number of the tourists are from the Ovation of the Seas cruise ship, but police could not confirm nationalities except to say New Zealanders and overseas visitors are among them.
It is believed there were fewer than 50 people on the island when the volcano exploded about 2.11PM (local time) on Monday afternoon.
Some reports say there were 24 Australians on or near the island at the time of the eruption.