At least five people were killed after the White Island or the Whakaari volcano in New Zealand erupted on Monday, police said, adding that the toll was likely to increase as a number of people were still unaccounted for.
National Operation Commander Deputy Commissioner John Tims told the media that the victims and the missing persons were both New Zealanders and tourists from the Ovation of the Seas cruise ship, The New Zealand Herald reported.
Tims added that the nationalities of the tourists could not be immediately confirmed.
So far, 18 people have been rescued; all have who have burn injuries to some degree.
The police have no information if the missing persons were alive or dead, Tims said, adding that further eruptions were possible.
The police are unsure exactly of the number of people who remain on the island, but have said that it was in double digits.
The force was also unsure of their wellbeing because no communication has yet been established.
"The experts that we've spoken to have said it is unsafe for us to go on that island. 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," the Deputy Commissioner said.
The island is currently covered in ash and volcanic material.
Ken Gledhill from GeoNet, the country's geological hazard information centre, said: "It's not a particularly big eruption, almost like a throat-clearing eruption, and that's probably why material won't make it to the mainland".
Smoke from the eruption, which took place at 2.11 p.m., went around 12,000 ft in the air, he said, adding that it has quietened down, but could not ascertain if there would be another eruption in the next 24 hours, reports The New Zealand Herald.
Images from the crater rim just minutes before the eruption show people walking close to the crater.
Meanwhile, Prime Minister Jacinda Ardern told the media that an active police search and operation was underway.
"All our thoughts are with those affected at this stage," she said.
The uninhabited White Island, which sits 48 km east of North Island, is known for its volcanic activity.