All victims of New Zealand's White Island volcanic eruption identified

All victims of the White Island volcanic eruption have now been identified, New Zealand police said Tuesday, as they formally named two Australians and an American among the deceased.

The explosion at the popular adventure tourist destination on December 9 killed 18 people, with another 17 receiving intensive treatment for severe burns.

Following lengthy forensic examination, the latest dead to be named were two Australians -- Richard Aaron Elzer, 32, and Julie Richards, 47 -- and a US citizen with Australian residency -- Barbara Jean Hollander, 49.

Police also for the first time identified two victims whose bodies have not been recovered -- Australian Winona Jane Langford, 17, and New Zealander Hayden Bryan Marshall-Inman, 40.

"The DVI (disaster victim identification) process is now complete," police said in a statement.

Search teams still hope to find the remains of Langford and Marshall-Inman, which are believed to be in the water off White Island, but police said poor weather early Tuesday was hampering efforts.

A Police Eagle helicopter left for the island in the early morning, but was forced to turn back. A dive squad searching the waters around White Island remained onshore.

All the dead and missing have now been identified and named publicly, barring one victim who died over the weekend in a Sydney hospital, whose family requested his details remain private.

At least 12 of the 18 fatalities were Australians, while another three were US citizens living in Australia.

Media reports said the man who died in Sydney was an Australian national and officials have said those being sent to Australia for treatment were either nationals or permanent residents.

The other two dead were New Zealanders working as tour guides on New Zealand's most active volcano White Island, also known as Whakaari.

A total of 47 day-trippers and guides were on the island when it erupted, hailing from Australia, the United States, Britain, China, Germany, Malaysia and New Zealand.

Authorities are examining why tour operators were allowed to take travellers onto the volcano's rim just days after scientists had raised its threat level.

However, Prime Minister Jacinda Ardern warned this week that the investigation could take up to a year.