WHAKATANE (AFP) -- Tales of heroism, devastation and horrifying injuries emerged Tuesday after New Zealand's smouldering White Island volcano exploded, killing an estimated 13 people.
Prime Minister Jacinda Ardern said five people had died and eight more were presumed dead after Monday's eruption, while dozens of injured had been airlifted to hospitals across the country.
Among the 47 people caught on the island during the sudden eruption were tourists from Australia, the United States, Britain, China, Germany and Malaysia, as well as local tour guides.
Amid questions over why tourists were allowed to visit the volcano, police announced a criminal investigation into the circumstances of the deaths and injuries.
Ardern praised the crews of four rescue helicopters for landing on the island soon after the eruption.
"Those pilots made an incredibly brave decision under extraordinarily dangerous circumstances in an attempt to get people out," she told reporters.
Intensive care paramedic Russell Clark was among those dispatched by helicopter to the caldera, which sits semi-submerged 50 kilometres (30 miles) out to sea.
There he found an "overwhelming" and "shocking" scene of devastation.
"We didn't find any survivors," he told TVNZ, remembering a dust-covered helicopter grounded with its rotor blades damaged.
"It was like.. I've seen the 'Chernobyl' mini-series and it was just everything was just blanketed ash.
"I can only imagine what it was like for the people there at the time -- they had nowhere to go and an absolutely terrible experience for them."
New Zealander Geoff Hopkins' tour boat was leaving the island when a huge plume burst from the volcano -- at what scientists said was supersonic speed -- followed by a "menacing" and fast-moving cloud of grey ash.
Despite the danger, Hopkins said the boat moved closer to the shore after seeing survivors who had jumped from the island into the sea to escape.
"I don't think there was anyone that came off who wasn't badly burnt," he told the New Zealand Herald, describing how victims screamed and went into shock as fellow tourist tried to tend to their blistered skin.
Top New Zealand health official Pete Watson said 27 of the 34 survivors were being treated for burns to more than 71 percent of their bodies.
"It's important not to underestimate the gravity of the injuries suffered," he said.
After an initial rush, concerns about further eruptions, poisonous gases and choking ash stalled efforts to recover bodies.
The risks were underscored Tuesday when a large-but-harmless 5.0 magnitude earthquake struck to the east of the disaster zone.
'Very hard day'
Ardern said New Zealanders were mourning alongside those from overseas tourists caught up in the disaster.
"To those who have lost or are missing family and friends, we share in your unfathomable grief and in your sorrow," the 39-year-old prime minister said, just months after managing another national crisis during Christchurch's deadly twin mosque attacks.
Many of the victims are believed to be Australian and Prime Minister Scott Morrison warned his compatriots to brace for the worst.
He said there were fears that three of the five dead were Australian, and another eight citizens were unaccounted for.
"This is a very, very hard day for a lot of Australian families whose loved ones have been caught up in this terrible, terrible tragedy," he told reporters in Sydney.
The Malaysian government said one if its citizens had died and two British women were confirmed to be among those injured.
The eruption at White Island -- also known as Whakaari -- occurred on Monday afternoon, thrusting a thick plume of white ash 3.6 kilometres (12,000 feet) into the sky.
When the blast occurred, it 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.
The island in the picturesque Bay of Plenty attracts more than 17,000 visitors every year.
But the threat level at the volcano had been raised in recent days, leading to questions about whether it was safe for tour groups to visit.
New Zealand police indicated that would be one focus of their investigation.
"I can confirm now that we will commence a criminal investigation into the circumstances of the death and injuries on White Island," deputy commissioner John Tims told reporters. (AFP)