A pale cloud of steam and smoke lingered menacingly Tuesday over White Island, just off the coast of New Zealand, where just one day earlier a volcano's eruption left several tourists dead, many more injured and an entire country rattled by tragedy.

By Tuesday evening local time, authorities had confirmed that another victim died at a nearby hospital, bringing the death toll to six. That number is likely to rise in the coming days — with eight people "missing and presumed deceased" and more than two dozen others from several countries having suffered "very severe injuries."

In some cases, police say that those injuries — most including significant burns to their skin and lungs — have caused such damage that simply identifying the victims has become a "complex matter."

"The scale of this tragedy is devastating," New Zealand Prime Minister Jacinda Ardern told lawmakers Tuesday. She said police and military personnel have been spearheading the search-and-rescue operations, which have been impeded by continuing volcanic activity on the island. "However, no signs of life have been detected in the aftermath of the eruption."

"We know, too, there will be bigger questions in relation to this event," the prime minister added. "These questions must be asked, and they must be answered."

Perhaps foremost among those questions: Why, exactly, were 47 people — many of whom were tourists, from as far afield as the U.S. and Germany — on an island that boasts New Zealand's most active volcano during a period of known volcanic activity?

For weeks, volcanologists at the country's geological hazards monitor had been warning of increased activity at the site. In mid-November, they bumped the official volcanic alert to Level 2 (out of five), meaning they expected the possibility of "eruptions of steam, gas, mud and rocks."

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A sign at the Whakatane wharf advertises guided tours of the White Island volcano. Officials had recently released alerts warning that it was more active than usual.

"These eruptions can occur with little or no warning," GNS Science volcanologist Michael Rosenberg explained in the bulletin.

The Buttle family has owned White Island, also known by its Maori name, Whakaari, for upwards of eight decades. According to the New Zealand Tourism Guide, the Buttles appointed White Island Tours to custodianship of the island about 22 years ago, and access to the area is controlled with permits.

The chairman of White Island Tours, Paul Quinn, told local media that the company took some 18,000 people to the island last year alone. He said that the company is in regular communication with GNS Science and that it routinely takes people to the island under Level 2 alerts, which it interprets as "safe" conditions still.

"We take our health and safety responsibilities very seriously," Quinn said, noting that two members of the tour operator's staff are among those still unaccounted for. "This is a big tragedy unfortunately for us."

New Zealand's workplace safety regulator, WorkSafe, announced Tuesday that it was opening an investigation into the deadly incident.

New Zealand police initially mentioned a criminal investigation of its own, but it walked that comment back within hours. Instead, law enforcement clarified, the investigation now open is "on behalf of the Coroner" and will be carried out in tandem with the WorkSafe probe. "It is too early to confirm whether there will also be a criminal investigation," police explained in statement.

Of the 47 people who were on the island at the time of the eruption, authorities say 24 hailed from Australia and nine from the U.S. Other visitors were from China, Malaysia, Germany, the U.K. and New Zealand.

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Mourners left floral tributes on a fence at the Whakatane wharf Tuesday, grieving for the victims of the eruption on White Island in New Zealand's Bay of Plenty.

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