Whakatāne Hospital needed to use every single bedspace and all its resources to deal with the first victims from the eruption on Whakaari/White Island.
Staff have spoken at a press conference outside the hospital. Health Minister David Clark and Police Minister Stuart Nash also spoke at the stand-up.
Whakatāne Hospital medical leader Dr Heike Hundemer said staff at the hospital held mass casualty training exercises, but what they were faced with on Monday was "beyond comprehension".
While they would normally have about six nurses and two doctors in the ED, on Monday there was about 100 staff, and they used every resource and bed space to care for the victims coming in, said Dr Hundemer.
"Monday is beyond anything we would have anticipated. I've never seen this number of critically injured patients coming into an emergency department in such a short space of time."
She said staff were affected by what they saw, and that they knew some of those they were treating or who had died.
Watch the press conference here:
Clark said he had met with staff at Whakatāne Hospital about how Monday's eruption affected them, and it was clear New Zealanders should be proud of how the health system responded.
Nash acknowledged to families that communication between families and commander HQ had not been as good as it should have been.
He said a better process was now being put in place to rectify this.
Nash said it was the number one priority for police to recover the bodies on the island, but it must be done in a way that minimised the risk to those who would be involved in the operation.
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.
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.
Follow the day's events in RNZ's live blog