Police in New Zealand are planning a mission to volcanic White Island on Friday to retrieve bodies of people killed in this week's eruption, while the known death toll from the disaster climbed to eight, with two people dying in the hospital.

Eight more people are missing and presumed dead, buried under ash and debris from Monday's eruption. More than 20 people are in the hospital, many with severe burns, while seven others have been transferred to burns units in Australia.

"I can now confirm that we are finalizing a plan to recover the bodies from Whakaari/White Island tomorrow morning," police Deputy Commissioner John Tims said in a statement on Thursday, adding families will be briefed on the operation.