By the Associated Press

WHAKATANE, New Zealand — Experts said geothermal activity on a New Zealand volcanic island increased significantly on Wednesday, dealing a blow to relatives waiting for crews to recover the bodies that remain there following a deadly eruption two days earlier.

Volcanic tremors rose in the morning, accompanied by an increase in the amount of steam and mud being released at White Island, the GeoNet seismic monitoring agency said.

“We interpret these signals as evidence of continued high gas pressures within the volcano,” the agency said. “The situation remains highly uncertain as to future activity. Eruptions in the next 24 hours are still likely to occur.”

Six deaths were confirmed after Monday’s eruption. Five people died at the time of the blast or soon after, while a sixth person died Tuesday night at an Auckland hospital.

Another eight people are believed to have died, with their bodies remaining on the ash-covered island for now. And 30 people remain hospitalized, including 25 in critical condition. Many of the injured suffered severe burns.

Bruce Bird, an acting assistant police commissioner, said they were monitoring the situation hour by hour.

“Safety for our staff is a huge priority for us,” Bird said. “And we’ve got to get this right.”

Bird said they had deployed a drone over the island to measure gas levels after strong winds had thwarted those attempts on Tuesday.

But helicopter pilot Mark Law said the delay was hard to understand and that if he was making the decision, he would leave immediately.

“It would take 20 minutes to get out there. We know where they are,” he said, referring to the bodies. “Then we could bring them home.”

Survivors from the Monday eruption ran into the sea to escape the scalding steam and ash and emerged covered in burns, said those who first helped them.

The tragedy will have an ongoing effect on the town of Whakatane, which road signs tout as the gateway to White Island. As well as being an important tourist draw for the 20,000 people who live here, the volcano has an almost mystical significance, its regular puffing a feature of the landscape.

Whether the island will ever host tourists again remains uncertain after the horrific tragedy that unfolded when the volcano exploded a little after 2 p.m. Monday.

Geoff Hopkins was in a boat offshore after visiting the island with his daughter, the tour a 50th birthday present for him. He told the New Zealand Herald the eruption at first looked beautiful but quickly turned menacing.

As injured people were transported onto their boat screaming in pain, Hopkins and his daughter Lillani poured fresh water onto them, cut them out of their clothes and tried to keep them calm.

He told the Herald they were horrifically burned on their exposed skin and faces, even under their clothes.

In all, police believe there were 47 visitors on the island at the time. They say 24 were Australian, nine were American and five were New Zealanders. Others were from Germany, Britain, China and Malaysia. Many were passengers aboard the Royal Caribbean cruise ship Ovation of the Seas.

The first confirmed death was of a local man, Hayden Marshall-Inman, a guide who had shown tourists around the island.

Former Whakatane Mayor Tony Bonne said Marshall-Inman was a keen fisherman and well-liked. He was so kind, Bonne said, that he would often leave extra money at the grocery store for those he knew were struggling to pay.

Many people were left questioning why tourists were still allowed to visit the island after seismic monitoring experts raised the volcano’s alert level last month.

“These questions must be asked, and they must be answered,” Prime Minister Jacinda Ardern said in Parliament.

New Zealand’s Deputy Police Commissioner John Tims said Tuesday that police were opening a criminal investigation into the deaths that would accompany an investigation by health and safety regulators.

But hours later, police put out a statement saying that while they were investigating the deaths on behalf of the coroner, “To correct an earlier statement, it is too early to confirm whether there will also be a criminal investigation.”

Australian Prime Minister Scott Morrison said 11 Australians are unaccounted for and 13 were hospitalized. Three Australians were suspected to be among the initial five confirmed dead, he told reporters in Sydney. “I fear there is worse news to come,” Morrison said.

Relatives of a newlywed American couple say the husband and wife were severely burned. Barbara Barham told The

Washington Post that her daughter Lauren Urey, 32, and son-in-law Matthew Urey, 36, from Richmond, Virginia, were on a honeymoon trip.

White Island, also known by the indigenous Maori name Whakaari, is the tip of an undersea volcano about 50 kilometers (30 kilometers) off New Zealand’s main North Island.

New Zealand’s GeoNet seismic monitoring agency had raised the volcano’s alert level on Nov. 18 from 1 to 2 on a scale where 5 represents a major eruption, noting an increase in sulfur dioxide gas, which originates from magma. It also said volcanic tremors had increased from weak to moderate strength. It raised the alert level to 4 for a time after Monday’s eruption but lowered it to 3 as the activity subsided.

At least 10 people were killed on the island in 1914 when it was being mined for sulfur. Part of a crater wall collapsed, and a landslide destroyed the miners’ village and the mine itself.

The island became a private scenic reserve in 1953. Daily tours allow more than 10,000 people to visit every year.

“Tourism has been a growing market, and White Island has been an anchor for that,” Bonne said. “It’s something unique that pulls people from all around the world.”

He said it was sad to think that might all now come to a stop.