The Whakaari, or White Island, volcano erupted on Monday afternoon.

Brodie Rafferty, 30, is on the Royal Carribean cruise with his mum Katrina, step-dad Richard and two younger brothers Garth and Coen.

The family had ventured ashore on Monday for a day trip to Rotorua but were shocked to hear of the tragedy when they returned to the cruise liner later in the afternoon.

"Everything was normal until yesterday (Monday). We went for a drive as a family to Rotorua and on the way back we saw a heap of police vehicles travelling towards the area of White Island," Mr Rafferty said from the ship on Tuesday.

The scale of the catastrophe has reverberated around the world with more than 100 names added to a list established by the New Zealand Red Cross of people being sought by family and friends.

It's believed up to three of those confirmed dead are Australians. Another eight, all believed to be Australians, are missing or unaccounted for.

Some 34 people, including 13 Australians, were rescued and taken to hospital suffering burns.

Of these, 31 remain in hospital while three have been discharged.

The Australians caught up in the blast are believed aged between 17 and 72.

Read more: NZ volcano: Names of missing Australians

"It is all fairly normal here (on the ship) at the moment. We don't know if we will be in this port for the rest of scheduled dates. We're due in Sydney, then back home next Monday but nobody knows what's happening even with remaining stops."

Mr Rafferty said he has been told five people have died, but cruise staff are not confirming how many of those may have been travelling with them.

Royal Caribbean, owner of Ovation of the Seas, issued a statement saying the ship would stay in the nearby port of Tauranga "until we learn more about the situation".

The island in the Bay of Plenty offers some of New Zealand's most lively geo-thermal activity with steam from the volcano's main vent sometimes visible from the mainland some 48 kilometres away.

A forensics team from the Australian Federal Police is on its way to New Zealand to help identify victims.

Australia is also sending extra consular staff to support those affected, AAP reported.

"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," Prime Minister Scott Morrison told reporters in Sydney on Tuesday morning.

While you're with us, you can now receive updates straight to your inbox from the Port Macquarie News. To make sure you're up to date with all the news, SIGN UP HERE.