The total number of deaths could still increase given that there are 20 people injured, most of them in a serious condition, Efe news reported.
The two latest victims, who died on Wednesday in a hospital, were brothers, aged 13 and 16, from Australia.
New Zealand police on Wednesday released the names and nationalities of nine of the 14 people who were believed to have died.
Australia's Prime Minister Scott Morrison said at a press conference that they had started the process of transferring five injured Austral and they hoped to carry out another seven evacuations in the next 24 hours.
On Wednesday, geological activity control group GeoNet warned that volcanic activity on Whakaari Island had increased significantly, and that the alert level remained at 3 on a scale of 5.
As a result, the authorities have not been able to return to the island, owing to safety reasons.
Police Minister Stuart Nash told the media that their priority was to get the victims out of the island but they also had to evaluate the risks.
On its part, GeoNet warned of a 40 to 60 per cent chance of a fresh eruption in the next 24 hours.
The first volcanic eruption occurred on Monday afternoon when 47 tourists were visiting the privately-owned island, which is located 48 km to the northeast off the coast of North Island.
Among the 47 tourists were people of various nationalities: 24 Austral, nine Americans, five New Zealanders, four Germans, two Britons, two Chinese and one Malaysian.
Whakaari - a 321 metre-high volcano, which has 70 per cent of its structure hidden below sea level - is considered one of New Zealand's most active volcanoes and is a major tourist attraction.
Located at the southeastern end of the Pacific Ring of Fire, Whakaari last erupted in 2016 without causing any fatalities.
The deadliest incident at the site occurred in 1914 when 10 miners died as a result of a landslide caused by the collapse of part of the volcano's crater.
( With inputs from IANS )