The site was still too dangerous hours later for police and rescuers to search for the missing.
Police Deputy Commissioner John Tims said the number of those who remained missing was in the double digits but he couldn’t confirm an exact number. He said there were fewer than 50 people on the island when it erupted and 23 had been taken off, including the five dead.
Tims said experts had told them the island remained unstable but search and rescue teams wanted to get back as quickly as they could. He said there had been no contact with any of those who were missing.
He said both New Zealanders and overseas tourists were among those who were dead, missing or injured. He said most of the 18 who survived were injured and some had suffered severe burns.
Some of those involved were guests from the Royal Caribbean International cruise ship Ovation of the Seas.
“A number of our guests were touring the island today,” the company said. “We will offer all possible assistance to our guests and local authorities. Please keep all those affected in your prayers.”
The cruise ship, which had left from Sydney last week, was scheduled to sail to the capital Wellington on Monday night, but the company said it would instead remain in the Tauranga port overnight until it learned more on the situation.
Prime Minister Jacinda Ardern said she was traveling to the region late Monday. She said the incident was “very significant.”
“All our thoughts are with those affected,” she said.
Brad Scott, a volcanologist with research group GNS Science, said the eruption sent a plume of steam and ash about 12,000 feet into the air. He said it had also affected the whole of the White Island crater floor.
The GeoNet agency, which monitors volcanoes and earthquakes in New Zealand, at first raised its alert level to four, on a scale where five represents a major eruption. It later dropped the alert level back down to three. Scott said that was because the eruption wasn’t sustained beyond the initial blast.
White Island sits about 30 miles offshore from mainland New Zealand. Already people are questioning why tourists were still able to visit the island after scientists recently noted an uptick in volcanic activity.
GeoNet raised the alert level on White Island from one to two on Nov. 18, noting an increase in the amount of sulfur dioxide gas, which originates from magma deep in the volcano. It also said at the time that over the previous weeks, the volcanic tremor had increased from weak to moderate strength.
Scott said the alert level was often raised and then later dropped again without any eruption. He said there hadn’t been any major incidents with tourists visiting the island in the past, although there had been some close calls.
Scott said it was not for him to say whether the island was safe enough to host tourists immediately before Monday’s eruption.
Ardern said the focus remained on the search and rescue mission for now and questions about whether tourists should be visiting would be addressed later.
“In the scheme of things, for volcanic eruptions, it is not large,” said Ken Gledhill from GeoNet. “But if you were close to that, it is not good.”
White Island is northeast of the town of Tauranga on North Island, one of New Zealand’s two main islands. Police were asking people to avoid areas on the North Island that were close to the eruption, including the Whakatane Heads and Muriwai Drive areas.
GeoNet said White Island is New Zealand’s most active cone volcano and about 70% of the volcano is under the sea.
Twelve people were killed on the island in 1914 when it was being mined for sulfur. Part of a crater wall collapsed and a landslide destroyed the miners’ village and the mine itself.
The remains of buildings from another mining enterprise in the 1920s are now a tourist attraction, according to GeoNet.
The island became a private scenic reserve in 1953, and daily tours allow more than 10,000 people to visit the volcano every year.
The island is also known by the indigenous Maori name Whakaari.