An erupting volcano forced a conservation team to abandon a missing colleague on a South Pacific island Friday as they fled spewing ash, steam and mud.

A helicopter evacuated the five conservation workers from Raoul Island, a nature reserve in New Zealand's remote Kermadec Islands.

A sixth employee of the government's Conservation Department, aged in his early 30s, went missing "after going on a routine mission to check the water temperature of the lake," said department regional manager Rolien Elliot.

Workers check the water temperature to try to predict eruptions.

Two staff members tried to search for the missing worker but had to retreat because the eruption made the track "impassable with fallen trees and ash," she said.

Helicopter pilot John Funnell told TV One there was devastation in the area around Green Lake, one of the island's three main craters. Bush and vegetation were blown away by the force of the eruption. The area was coated in mud and ash up to 16 feet deep.

The eruption lasted about 30 minutes starting at 8:21 a.m., said GNS Science, the country's main geological science group. It followed strong earthquakes that began Sunday night, GNS Science said.

The volcano threw out mud, rocks and a plume of steam, but no lava or molten rock.

The rescued conservationists — three men and two women — were "quite strained" by the ordeal and because they had to leave their colleague behind, the helicopter pilot said.

The last known eruption on Raoul Island, about 625 miles northeast of the New Zealand city of Auckland, was on Nov. 21, 1964, from a vent close to Green Lake. There were no casualties.

The Kermadec Islands are formed by a string of young volcanos that spring up to 26,000 feet from the ocean floor.