New Zealand's Prime Minister Jacinda Ardern expressed "unfathomable grief" Tuesday for tourists caught in a deadly eruption at the White Island volcano, where five people have died and eight more are feared dead.
Ardern held out no hope for the eight people still missing after Monday's tragedy, saying overnight aerial reconnaissance flights had found no signs of survivors.
"The focus this morning is on recovery and ensuring police can do that safely," she told a press conference.
Among the missing and injured are tourists from Australia, the United States, Britain, China and Malaysia, as well as New Zealanders who were acting as guides.
"To those who have lost or are missing family and friends, we share in your unfathomable grief and in your sorrow," Ardern said.
"Your loved ones stood alongside Kiwis who were hosting you here and we grieve with you."
In addition to the five dead and eight missing, Ardern said 31 people who were on the island during the cataclysm were in hospital with various injuries, including serious burns.
In the hours after the eruption, police had determined the risk was too great for on-land rescues.
Police spokesman Bruce Bird said a helicopter has scoured the area for 45 minutes, checking if anyone was still alive -- without success.
Safety concerns have stalled the effort to recover bodies.
"We will only go to the island when it is safe to do so for our people," said Bird.
A large proportion of the victims are thought to be Australian.
At the time of the eruption, the island was being visited by a group of more than 30 people from a Royal Caribbean cruise ship, the Ovation of the Seas, which left Sydney on a 12-day voyage last week.
Prime Minister Scott Morrison said 24 Australians were among those on the volcano tour.
"We must prepare for some difficult news in the days ahead," he said.
Britain's high commissioner in New Zealand said two of its citizens were being treated.
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The eruption at White Island -- also known as Whakaari -- occurred just after 2:00 pm Monday (0100 GMT), thrusting a thick plume of white ash 3.6 kilometres (12,000 feet) into the sky.
The island is about 50 kilometres (30 miles) offshore in the picturesque Bay of Plenty and attracts about 10,000 visitors every year.
Seconds before, live camera feeds showed a group of more than a half dozen people walking on the crater floor. Then the images went black.
The threat level at the volcano had been raised in recent days, and questions are already being raised about whether it was safe for tour groups to visit.
Cruise operator Royal Caribbean had sold a day trip to White Island as an "unforgettable" adventure to New Zealand's most active volcano, one that took visitors so close to the action they could require gas masks and hard hats.
White Island Tours said it "operates through the varying alert levels" but that "passengers should be aware that there is always a risk of eruptive activity regardless of the alert level."
Ardern said there were legitimate questions to be asked but they could wait until the emergency response was complete.
"The focus today is on providing critical care for those who have been injured," she said.
Scientists said there had been increased activity at the volcano over the past week -- but nothing to indicate an eruption was imminent.
"The eruption was unfortunate but not completely unexpected," said Jessica Johnson, a geophysicist at the University of East Anglia.
She said levels of activity "have been relatively high since September, and even more elevated over the last couple of weeks," with small earthquakes and more volcanic gas detected than usual.