The New Zealand Herald understands the man is Hayden Marshall-Inman, an experienced guide for White Island Tours.
Former Whakatane mayor Tony Bonne said he was "a young energetic man who's lost his life".
Friends and family have posted tributes to the man online, remembering the kind nature of the man who died "doing the one thing he loved."
Early today police released a statement that said no signs of life had been seen at any point of the numerous aerial reconnaissance flights over the island since the eruption.
"Police believe that anyone who could have been taken from the island alive was rescued at the time of the evacuation."
Based on the information they had, police do not believe there are any survivors left on the island, the statement said.
Travellers to White Island remembered Marshall-Inman as passionate and kind.
"Honestly, his kind spirit and warmth was my favorite part of our trip to New Zealand," one wrote.
Others remembered his smile and generosity.
"I worked at the Ohope 4 Square and whenever he came in and made a purchase he always gave us $5 to pay towards the next person's groceries, he had the kindest heart, it was never about him, he definitely created a ripple affect of happiness to others," a local wrote.
Marshall-Inman's employer, White Island Tours Limited, released a media statement late last night, saying it was "deeply saddened" at the volcano's significant eruption.
"Devastation is an understatement," Paul Quinn, Chairman for White Island Tours said.
"This is a terrible tragedy and our thoughts and prayers are with everyone who has been impacted."
Quinn said the company's immediate focus was on supporting the staff, manuhiri and respective whānau, who had been "significantly impacted were showing immense strength and courage."
Both New Zealand and overseas tourists were believed to be among the dead, a number of them from the Ovation of the Seas cruise ship.
Police said they were working to urgently confirm the exact number of those who died, further to the five that were confirmed as dead on Monday evening.
