WELLINGTON (REUTERS, AFP) - New Zealand Prime Minister Jacinda Ardern said on Monday (Dec 16) that official inquiries into last week's fatal volcano eruption could take up to a year, and will carry potential criminal penalties of up to five years in jail.

Ardern also announced an NZ$5 million (S$4.5 million) fund to help small businesses affected by the eruption, after New Zealanders held a minute of silence to honour the victims a week on from the tragedy.

The official death toll from the surprise eruption on White Island, also known by its Maori name of Whakaari, stands at 16. Two people whose bodies are believed to be in the waters around the island are still officially listed as missing. A further 26 people remain in hospitals in New Zealand and Australia, many in critical condition with severe burn injuries.

"There remains now questions to be asked and questions to be answered," Ardern told reporters in Wellington after she led the country in a minute of silence for the dead and injured, who included tourists from Australia, the United States, Germany, China, Britain and Malaysia.

At 2.11pm local time (9.11am Singapore time) - precisely a week since the eruption - offices and shops fell silent as New Zealanders remembered those killed by the eruption.

Flags flew at half-mast outside Wellington's distinctive "Beehive" Parliament building, while inside Prime Minister Jacinda Ardern suspended a Cabinet meeting and stood head bowed to quietly reflect on the disaster.

Announcing the gesture on Saturday, Ardern said: "Wherever you are in New Zealand, or around the world, this is a moment we can stand alongside those who have lost loved ones in this extraordinary tragedy."

Many of those affected were Australian and Ardern's counterpart in Australia, Scott Morrison, said his compatriots were also honouring the dead, injured and their loved ones.

Australian Foreign Minister Marise Payne met her New Zealand counterpart in Wellington on Monday to express Australia's thanks to emergency and medical crews.

Whakatane mayor Judy Turner said the authorities took grieving families out on boats to within a safe distance of the volcanic island to mark the event.

PROBE INTO TRAGEDY

WorkSafe, New Zealand's primary regulator for workplace related incidents, has opened a health and safety investigation, Ardern said, while the coroner is conducting a separate inquiry.

Worksafe can prosecute individuals and companies for breaches of health and safety laws, with penalties including fines of up to NZ$3 million and jail terms of up to five years, Ardern said.

A coronial investigation is automatically triggered in the event of a sudden, violent or unnatural death. A coroner can also make recommendations to prevent similar deaths in the future.

Ardern said the Worksafe investigation could take a year, while the coronial inquiry was "also likely to continue for some time.

The NZ$5 million support fund is expected to be distributed among businesses in Whakatane, the mainland coastal town that serves as the jumping off point for trips to Whakaari. Asked if operators of tours to the island would be among the beneficiaries, Ardern said that specifics had not yet been determined.

MORE VICTIMS NAMED

Police on Monday morning released the names of another four fatalities.

All four were Australian - Jessica Richards, 20, Jason David Griffiths, 33, Martin Berend Hollander, 48, and Kristine Elizabeth Langford, 45.

It brings the number of Australians identified as fatalities in the eruption to eight, along with two US citizens who had permanent residency in Australia.

'DAYS OR WEEKS'

The only other person identified so far is New Zealander Tipene James Te Rangi Ataahua Maangi, 24, who was working as a tour guide on the volcano last Monday when it blasted out a huge plume of ash, rock and superheated steam.

A total of 47 day-trippers and guides were on the island at the time.

Special forces troops retrieved six bodies from the island last Friday but the remains of two people have still not been found, despite a second land search on Sunday.

Police commissioner Mike Bush said the two bodies were believed to be in the water off White Island.

"We've been working with all the experts, including the harbour-master who knows those waters better than anyone, to try to predict where those persons might be," Bush told RNZ.

He said a helicopter was scouring the waters of the Bay of Plenty on Monday, with searches by police and navy divers to resume on Tuesday.

"We will continue the operation for as long as we have a chance of recovering those bodies," he said, adding in a separate interview to Auckland radio station Magic "it can take days and weeks".

Bush was confident all the dead currently being examined by forensic specialists would eventually be identified and their bodies returned to grieving families.

"That's progressing really well. It's just so important that we get it right and also that we do it as quickly as possible," he said.

POTENTIAL LIABILITY OF CRUISE FIRM

Many of those affected were passengers on the cruise liner Ovation of the Seas - owned by Royal Caribbean International - which berthed in Sydney early on Monday.

"(It was) a bit sombre," Australian man Troy, who did not give his surname, told Channel Nine television after completing the voyage across the Tasman Sea.

"The crew were really good and trying to stay upbeat but you could tell they were hurting. I think the captain was breaking down crying a fair bit."

Legal experts said last week they expected to see lawsuits filed in the US courts by injured passengers and families of those who died. Royal Caribbean's potential liability for the deadly excursion could hinge on whether the eruption was an unforeseeable "act of God," maritime lawyers told Reuters.

"We will to continue to provide ongoing support and services to them and their families during this difficult time," a spokesman for the company said in an emailed statement on Monday.