WELLINGTON — New Zealand marked one week since the deadly White Island eruption with a minute's silence Monday, as Prime Minister Jacinda Ardern warned grieving families they face a lengthy wait for answers.

At 2:11pm (0111 GMT) — exactly a week since the eruption — offices and shops fell silent as New Zealanders remembered the 16 international tourists and two local guides who died, along with at least 18 more now receiving intensive treatment for severe burns.

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

"Our thoughts continue to be with the families of those who have passed and those who are injured," she said.

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

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

However, Ardern said it would take time to determine why tour operators were allowed to take travelers onto the rim of an active volcano just days after scientists had raised its eruption threat level.

She said officials had advised her that a probe by workplace regulator WorkSafe New Zealand may take a year and a separate inquiry was "also likely to continue for some time".

"Look, as we've seen, inquiries can sometimes take more than that time, so it's not for me to judge whether that's an appropriate time frame," she said.

"They need to do their job properly and it needs to be properly considered."

Under New Zealand workplace law, individuals can face a maximum three years jail for reckless conduct resulting in death, while companies can be fined NZ$3 million (US$2 million).

The country also has a scheme called the Accident Compensation Commission, which covers victims' medical bills and provides modest compensation but does not allow civil suits seeking multi-million dollar damages payouts.

Ardern denied this had promoted a dangerous culture in New Zealand's adventure tourism sector.

Police on Monday 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. -AFP