Photo/Illutration In this combo made from two satellite images taken May 12, left, and Dec. 11, right, steam rises from the volcano on White Island off the coast of Whakatane, New Zealand. (Satellite image © 2019 Maxar Technologies via AP)

WHAKATANE, New Zealand--New Zealand medical staff were working around the clock Thursday treating severely burned survivors of a volcanic eruption that police said was believed to have killed 16 people.

The enormity of the task facing New Zealand's hospital burn units was clear when Dr. Peter Watson, a chief medical officer, said at a news conference that extra skin has been ordered from American skin banks.

Hospital personnel anticipated needing an extra 120 square meters of skin for grafting onto the patients, Watson said. Most of the survivors of Monday's eruption suffered critical burns and remain hospitalized.

The towering eruption of scaling steam and ash occurred as 47 visitors explored White Island, the tip of a mostly underwater volcano that's about 50 kilometers off New Zealand's North Island.

Police said Thursday an additional two people had died in the hospital, raising the confirmed toll to eight. Another eight bodies are believed to remain on the ash-covered island, where continuing volcanic activity has delayed their retrieval.

Authorities say 24 Australians, nine Americans, five New Zealanders, four Germans, two Britons, two Chinese and a Malaysian were visiting the island at the time of the eruption. Many were from a Royal Caribbean cruise ship that had left Sydney two days earlier.

New Zealand Prime Minister Jacinda Ardern said Thursday some injured Australians had been medically evacuated and such flights would continue. Australia previously said up to 10 such patients would be transferred to hospitals in Victoria and New South Wales states for further treatment.

New Zealand's GeoNet seismic monitoring agency lowered White Island's volcanic alert level to 2, noting there's been no further eruption since Monday, when the level had briefly been raised to 4. Its alert level since late Monday had been 3 on a scale where 5 signifies a major eruption.

A further eruption in the next day still remains a possibility, the agency said Thursday, noting volcanic tremors are rising and steam and mud were being vented regularly.