"That flame has actually ignited the escaped gas and it's caused a minor explosion."
Mr Johnston said other campers did a good thing when they put the man on a seat in the lake and submerged his burns.
He said it was fortunate the tents where the fire happened were canvas which was harder to ignite than nylon.
Nylon hiking tents would "go up in the blink of an eye".
It was also fortunate the fire happened where there was not a high density of tents.
Mr Johnston said the cylinder was properly certified.
"It's just for some reason the gas bottle wasn't turned off when [it] was turned off and that is still part of the investigation."
Camp manager Keith Waddell said the gas set fire to the surrounding area and clothes that were ready to be packed.
Mr Waddell said the park had firefighting hoses, not required in this case, it could have used to fight a fire involving tents or other property.
The park did not have the specialist foam equipment used by the fire brigade to cool LPG bottles that caught on fire.