The death toll from the Whakaari/White Island eruption has risen to 21 after another victim died in Middlemore Hospital last night.

Photo: Supplied / Lillani Hopkins

Police have confirmed another person has died as a result of injuries suffered in the eruption on 9 December.

The announcement brings the official death toll from the eruption to 21 people, 19 of whom died in New Zealand and two in Australia.

Police said the latest victim's name would be released after wider family have been informed.

The two bodies that were not recovered were those of Hayden Marshall-Inman, a New Zealander who was one of the White Island Tours guides, and 17-year-old Australian tourist Winona Langford. They have been officially listed as dead by the Chief Coroner.

Marshall-Inman was believed to have returned to the island from a boat, perhaps to rescue those still there. His brother Mark said there were footsteps showing he went back.

Langford's mother and father also died from the eruption, though her brother Jesse survived.

At the time of the eruption, 47 people were on the island including 38 cruise ship passengers.

Hospitals here and in Australia have needed an unprecedented amount of skin for dressing victims' extensive heat and chemical burns.

In an international effort, a quarter of a million square centimetres - the equivalent of 14 full human bodies' worth of skin - has been used to try save the lives of the injured. More is expected to be used from the inventory of about one million square centimetres, which is about half the area of a tennis court.