Firefighters dampen down hotspots at the reserve on Saturday.
Rotorua Fire Brigade senior station officer Richard Anastasi said the fire was called in at about 4.40pm with six units - three from Rotorua, two from Ngongotaha and one from Lake Okareka - attending the scene.
Mr Anastasi said the cause of the fire was unknown and was being treated as suspicious.
He said there were a number of large piles of wood in the reserve after the Rotorua Lakes Council cut down trees and scrub there recently.
"It's up to the police to investigate if they want to, but since we don't know the cause we are treating it as suspicious. It could have been some kids playing with matches, it could have been deliberately lit, or it could have been totally accidental."
He said the council had been contacted about reducing the size of the remaining piles of wood.
"It was quite a large pile and we had to use a digger to break it up.
"We have had a word with the council to try and minimise the risk up there as soon as possible. There's still a lot of cleaning up to do there and the longer it's there it will be more of a risk.
"There was no danger of it damaging property, but I was concerned as it was fairly close to a lot of gum trees. We did manage to cut it off as there was also a breeze going through there. We had it under control in an hour and spent a few hours to dampening it down."
Firefighters also used a thermal imaging camera to locate and put out hotspots.
He said it was a timely reminder for people to be very careful with a long hot summer forecast.
"People need to be aware there is a restricted fire period on now, especially in rural areas, where any fire needs a permit."