An 8-year-old boy is this morning fighting for his life in Auckland's Middlemore Hospital after falling into a Rotorua geothermal pool as hot as 100C.

Witness Anna Kare said the boy was screaming in agony and burned head to toe as a teenage boy carried him to his parents.

"The boy was yelling, 'My hands, my hands', and I saw all the skin on his hands peeling off," Mrs Kare said.

"I then saw the burns were all the way from his head to his feet. There was no mud on him so I don't think he fell into a mud pool, it was just water."

Mrs Kare said people started pouring cold water over the boy's body.

"There was screaming and yelling - it was just horrible.

"He would say, 'My feet, my feet', then after the water he was saying, 'My face, my face' then back to his hands again.

"My daughter was crying for hours ... She has already had nightmares about it."

Authorities do not know which of the pools at Rotorua's Kuirau Park the boy fell into or how he fell, and are relying on his family to fill in the blanks. The Boxing Day incident was revealed publicly yesterday.

Last night, his parents were at his side in the the intensive care unit at Middlemore Hospital. A hospital spokesperson this morning described his condition as critical.

A hospital spokesman yesterday said the boy was a Pacific Islander and his family did not speak English. An interpreter would be used to get more details about the boy, but until then, staff had limited information about him.

Emergency services were called to Kuirau Park about noon on Boxing Day.

The boy was taken to Rotorua Hospital and then flown by helicopter to Middlemore.

Westpac Waikato Air Ambulance pilot Grant Bremner said the boy was unconscious when he was transported.

"He was on a ventilator and on life support, he was severely burned," he said.

Rotorua District Council parks and recreation manager Garry Page said last night that mud and water geothermal pools could reach 100C - boiling point.

All the pools in the park were fenced off and carried warning signs.

He said the incident was still under investigation, but without information from the family, the council's hands were tied.

"We've gone as far as we can until someone can provide us with some information," he said. "Unless the family come forward and make contact with us, we won't know."

Mr Page said the incident was a reminder that people needed to take care in active geothermal areas and stay well clear of pools.

"There are signs all over the park warning people of the pools' dangerous geothermal nature and we have made every attempt to keep people out of them.

"We have cut sight lines so people can see into them but they still climb over the fences and put themselves at risk."

Only a few of the pools did not have mud, so the boy could have fallen into the geothermal lake.

Mr Page said hot-pool accidents were not common.

"As far as I can remember, the only times people have been hurt in the past 20 years or so were when people went beyond the safety barriers."

Mr Page urged people to contact the council if they saw any holes or damage to any safety barriers around hot pools so they could be repaired.

"It's no use telling us about it afterwards," he said.

Rotorua's hot pools have claimed several victims over the years, most recently in August last year when a 61-year-old man was found dead in a privately owned pool.

Two elderly men died in separate incidents while bathing in thermal pools during Rotorua holidays.

Phillip Stanley Binns, 77, of Nelson died in 2008 and Phillip John Ham, 88, of Takapuna, in 2007, both from cardiopulmonary congestion caused by hydrogen sulphide in the pools.