Another person injured in a volcanic eruption on a New Zealand island last week has died, police said, bringing the official death toll to 15 and the total number of likely dead to 17.

New Zealand police announced Saturday night local time that the person who died had been hospitalized after the eruption, which occurred shortly after 2 p.m. on Dec. 9, on White Island.

Two more people who are presumed dead remain unaccounted for.

On Friday authorities recovered six bodies from the island in a risky operation as the threat of another eruption remained.

The geological agency GeoNet said Friday that although the level of volcanic tremors has dropped, it remains very high compared to pre-eruption levels, and steam and mud bursts were continuing.

"Police remain focused on supporting families at this terrible time," New Zealand police Deputy CommissionerJohn Tims said in a statement about the new death.

Many of those injured suffered terrible burns.

Authorities had said earlier Saturday, before the injured person’s death was announced, that 15 people remained hospitalized in the country and 11 of those were in critical condition.

Thirteen others who were injured had been transported to Australia, the ministry of health said Saturday.

Searchers on Saturday continued to look for the body of one person seen in the water following the eruption, police said. The water around the island has been contaminated and visibility was said to be poor, creating challenging conditions.

White Island is roughly 30 miles off the coast of New Zealand's North Island and is known as a stratovolcano, characterized by continuous small-to-moderate eruptions over the past 150,000 years. Scientists say the volcano is difficult to predict, making it one of the most dangerous in the world.

About 47 tourists, including nine Americans, were visiting the island when the volcano erupted.

New Zealand police said they intend to open an investigation into surrounding events, including an inquest into health and safety issues for tourists and tour companies.

White Island is privately owned but became part of a scenic reserve in 1953, and daily tours bring more than 10,000 visitors each year, according to GeoNet's website. Around 70 percent of the volcano is underwater, and it is the largest volcanic structure in the country.

New Zealand Prime Minister Jacinda Ardern on Friday thanked those involved in the recovery and said her thoughts were with the victims' families.

"We know that reunification won't ease that sense of loss or grief because I don't think anything can," Ardern said in a statement. "But we felt an enormous duty of care as New Zealanders to make sure that we brought their family members back."