The son of two Australians injured in Monday's Whakaari/White Island eruption says the timeline for his parents' recovery is uncertain and they could face months in hospital.
Sydney couple Nick and Marion London, who are both in a critical condition, were flown back to Australia for treatment earlier in the week.
They have burns to 50 per cent of their bodies and internal chemical burns from breathing in toxic gases, Australia's Sydney Morning Herald reported.
They remain on life support and face an uncertain recovery timeline, son Matt told the newspaper.
"The road ahead no doubt will be very difficult with many up and downs," he said.