Two teenage boys have described harrowing scenes as they watched their 14-year-old friend become enveloped in a ball of flame after an explosion in Hamilton yesterday.

Ben Cleaver is in a critical condition in Auckland's Middlemore Hospital after suffering burns to 70 percent of his body in the explosion at his family's home in Rimu St, Maeroa. His family was at his bedside last night.

Kale Hoggart, 15, and Jack Pavich, 14, were in the container with victim Ben, 14, and his 11-year-old brother Troy. They were relaxing during a Fraser High School teacher-only day.

Waikato fire safety officer Ross Fleet said the boys then started "mucking around with a fuel container from the lawnmower".

"One of them (Ben) has been in the process of emptying the fuel contents into some sort of cup, and sometime after that he has lit a cigarette and he has burst into flames, and the furnishings around him have also caught fire."

Kale, Jack and Troy managed to escape the inferno. However, Ben was temporarily trapped in the container as flames wrapped themselves around him.

Troy ran screaming for help, alerting neighbour Paul Temple, and the boy's other friend, Jacob Stewart, also 14, who was asleep inside the house. Mr Temple helped pull Ben from the container before pouring water on his burns.

"He (Troy) came and said that his brother was on fire. I ran up and (Ben) rolled out of the container. I helped him out and then he fell on the ground. I told (Troy) to ring 111 ... he was feeling (burns), he was screaming."

Police praised Mr Temple's efforts in helping save the boy's life.

Speaking to the Times just minutes after the explosion, the boys appeared still in shock as they recalled the dramatic events.

"His whole body was on fire and then (Mr Temple) pulled him free. His whole body, his arms, his back...and all his clothes just stuck to him," Jacob said.

The burnt and melted remnants of Ben's hooded sweatshirt lay in the driveway just metres from the container.

The boy's engineer father, Kevin, told the Waikato Times yesterday they knew how serious Ben's condition was.

He said the container stored beds and household products.

Mr Cleaver and Ben's mother Linda, who works at Waikato Hospital, and other family members were packing yesterday afternoon before they headed off to Ben's bedside. They were too distraught to make any further comment.

Mr Fleet said although Ben had suffered horrific injuries, he knew he was receiving the best care around.

"I'm ever hopeful, given the firefighters (injured) at Tamahere (last year) and their recovery, I know that he's in the right hands."

- © Fairfax NZ News