A witness to a fatal accident near the Kaimai Range has recalled the events that unfolded when a campervan burst into flames on Saturday night

Mark Harris was travelling on Tauranga Road to go pig hunting in the Kaimai Range on Saturday afternoon when he saw the "old-style" campervan erupt in flames on the side of the road, near Matamata.

Bob and Doreen Appleton at the scene of Saturday's campervan fire on Tauranga Road near Matamata. Photo: George Heard/Fairfax NZ

The 26-year-old man recalls seeing a man hurl himself in flames from the burning campervan as Mark, and his mate Trardyn Lunn, rushed to help a screaming woman trapped inside.

"We smashed the back window and tried to get her out, but the fire just took over within seconds," says Mark.

"It was like a bonfire with about 20 litres of petrol on it. We definitely did all we could but it wasn't enough at the end of the day."

The burnt-out campervan believed to be at the centre of Saturday's fatal fire. Photo: George Heard/Fairfax NZ

Police confirmed a female passenger died at the scene.

A 72-year-old man, from Opotiki, who is understood to be the woman's husband, suffered serious burns to more than 50 per cent of his body.

Travelling behind the campervan was the injured man's brother.

Mark says the man's brother quickly rolled the injured man across the ground to put out the flames before they then helped him into Mark's ute and drove him a short distance to where Mark's father lives.

Mark's father and his partner, Carole Appleton, weren't home at the time but Mark arrived to find Carole's parents, Bob and Doreen Appleton, there feeding the pets.

"We'd only just arrived to give the chooks and cats a feed and all of a sudden Mark and his mate roar up the drive and yell out they need water," says Bob Appleton.

"You could see this guy was badly burnt but he managed to stumble inside with the boys' help and they sat him in the bath. We then just started pouring cold water over him and had buckets going. I even stuck the hose through the window just so we could fill the bath up quickly."

They cut the injured man's clothes off in an effort to bathe his burns in water.

St John ambulance staff arrived shortly afterwards and praised the young men's actions.

"Everyone was just so impressed that these young guys knew exactly what to do and were so calm about it. This poor chap didn't say a word and never mentioned his wife. You could tell he was in shock," says Bob.

St John staff wrapped the man's burns in plastic wrap before the Tauranga-based Trustpower TECT Rescue Helicopter arrived and transported him to Waikato Hospital.

His condition was described as critical on Sunday.

Bob Appleton says the injured man's brother also suffered burns to his arms and hands after trying to put out the man's burning clothes.

The scorch marks on the roadside bank where the campervan came to a stop indicate how severe the fire was, he says.

"It all just shows how fragile human life can be. These people could have been going along enjoying themselves and then this happens. This poor chap never said a word, he just sat in the bathtub with his boots on as we poured water on him."

Mark, a dairy farmer from Te Awamutu, says instincts took over when he came across the fire and remembers being told to treat a burn with running cold water.

He says his mind was constantly retracing the events of Saturday.

"Everything happened so fast and you definitely keep going over it in your head. You just don't expect to see a campervan catch fire like that.

"Within seconds the flames were higher than the campervan and were going up the bank and tree. Even though the driver got out quickly, even he nearly didn't make it."

The burnt campervan was transported to a salvage depot in Hamilton.

Mark suspects a fuel leak could have started the fire, saying a fire strip could be seen where the campervan crossed the road into the ditch.

The vehicle had stopped behind a roadworks truck when it caught fire.

Carole Appleton says her mother contacted her on Saturday evening to tell her about the fire.

She says Mark's actions were typical of a person who always thought of others.

"He's a level-headed farmer and he's very kind and gentle. He always looks out for other people and in a situation like this he and Trardyn wouldn't have hesitated to help."

Reporting- Aaron Leeman, Stuff.co.nz