The official death toll released by New Zealand authorities is eight, following two deaths overnight in hospital, one in Middlemore Hospital and the other in Waikato. Eight others on the island are presumed dead.
Matthew Hollander, a Year 8 student, and Berend (Ben) Hollander, a Year 10 student, both sustained injuries in the eruption. The pair attended Knox Grammar School in Wahroonga, an Upper North Shore suburb of Sydney.
Headmaster of the school, Scott James, wrote in a letter to parents that it was a devastating loss for the community.
"Matthew had a close circle of friends and was popular amongst his peers. He was always enthusiastic about life and actively involved in school and year group activities," he wrote.
"Ben was actively engaged in sports ... was a compassionate and enthusiastic student, with an interest in software design. 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."
James said the boys' parents are unaccounted for.
There are 23 people receiving hospital care in New Zealand - and up to five others have been airlifted to Australian hospitals. The extent of their injuries is such that skin is being brought in from Australia and the United States for grafts.