Dangers posed by a volatile South Pacific volcano are preventing searchers from looking for a missing conservation worker feared killed when it erupted last Friday, officials said Wednesday.

A 12-member team on remote Raoul Island, 620 miles north of New Zealand, would likely be unable to recover the body of Mark Kearney, who was checking the volcano's crater lake temperature when it exploded.

Kearney, 23, has been missing since then, and the eruption probably buried him under 16 feet of mud and ash.

Police, vulcanologists and eight conservation staff — including five who were evacuated Friday — arrived at the island Tuesday to check conditions and search for Kearney.

"At this stage we will not be looking at a recovery operation primarily because the level of the lake where Mark would have been at the time has risen ... six to eight meters [19-26 feet]," Conservation Department area manager Rolien Elliott said.

The lake level had risen another 6.5 feet since Tuesday, she said.

"So, it's not physically possible to get to area where Mark would have been — and it's far too dangerous," she told National Radio.

Vulcanologists reported that the volcano remained volatile after confirming the significant rise in the water level of its crater lake.

The same phenomenon occurred shortly before the volcano's last major eruption in 1964.

Vulcanologist Brad Scott said Wednesday there was no problem with the assessment team being on the island, but "at the moment approaching the crater lake and going there is just not a starter."

Department spokeswoman Liz Maire said the area near the crater lake may be off limits for "many months."

"It is going to take a lot of weathering and time for that area to settle down to a safe level. The area is still classified as potentially volatile," she added.

Elliott told National Radio that "there's no doubt in my mind, after talking to the crew" on the island that Kearney is dead.

"Now with everybody having seen the site [of Friday's eruption] there's the very, very remotest chance that Mark could still be alive," Elliott said.

The island, a nature reserve with a weather and volcanic activity monitoring station staffed by six people year-round, was closed to all visitors by the department after the eruption.

The surrounding seas make up New Zealand's largest marine reserve.

The Kermadec Islands are formed by a string of volcanoes which reach up to 26,000 feet from the ocean floor.