Sydney brothers Matthew and Berend Hollander were the latest victims to be named after the teenagers died in hospital from burns sustained in Monday's eruption on White Island.

Prime Minister Scott Morrison has said 10 Australians are "missing and presumed deceased" but it's unclear how many of those might overlap with the eight deaths already confirmed by family and friends.

"In the days ahead, there will be worse news," he warned on Thursday.

The volcano remains volatile, amid fears another large explosion is imminent, but New Zealand police have announced they will attempt to retrieve eight bodies from the island on Friday morning.

"We know that with quite a number of persons still on the island, understood to be deceased, that we will just have to be patient while circumstances are continually reviewed," Mr Morrison said earlier.

When the recovery occurs, "there will be the very grim task of identification".

Five injured Australians have been flown home, with seven more to follow in the next 24 hours, leaving just one Australian in a New Zealand hospital.

Matthew Hollander, 13, and his brother Berend, 16, have been remembered fondly by their Sydney school Knox Grammar, while their parents Martin and Barbara are still unaccounted for.

Knox headmaster Scott James said the death of the boys was a "devastating loss for our community".

"Matthew had a close circle of friends and was popular amongst his peers," Mr James said.

"Ben's engaging smile and quirky sense of humour made him a good mate to his close group of friends and a welcome member to every classroom."

Coffs Harbour couple Karla Matthews, 32, and Richard Elzer, 32, were confirmed dead on Wednesday night, along with friend Jason Griffiths who died in hospital with burns to 80 per cent of his body.

The trio had been travelling with six friends on the Ovation of the Seas cruise ship when they took a tour of White Island.

Their six surviving friends - Alex, Daniel, Ellie, Leanne, Paul and Samantha - said they were "devastated" to learn the trio were visiting the island when the eruption occurred.

Adelaide man Gavin Dallow, 53, has also died, while his family is mourning his 15-year-old stepdaughter Zoe Hosking who is missing presumed dead. Her mother Lisa Dallow is fighting for life in hospital.

Brisbane woman Julie Richards, 47, and her daughter Jessica, 20, have been remembered by family as an adventurous pair.

Melbourne woman Krystal Browitt is on the New Zealand police list of those missing, presumed dead on the island. Ms Browitt was reportedly on the cruise with her family to celebrate her 21st birthday

Sydney family Anthony and Kristine Langford, son Jesse, 19, and daughter Winona, 17, are also missing.

Australian Associated Press