Rotorua Lakes Council principal rural fire officer Richard Horn said they were still to determine what caused the fire in Sulphur Bay yesterday afternoon.
"There are still a few active hot spots through the area including a few sulphur fires," Mr Horn said.
A firefighter was on standby at the scene throughout the night to make sure the fire was contained and to ensure there were no re-ignitions.
A Rotorua Daily Post reporter at the scene this morning said the area looked dry, burnt and there was a potent smell.
The fire started about 3.30pm and quickly whipped up, with flames spreading 500m to 1km gutting bush and smaller trees.
There were reports of ash reaching as far away as Lynmore.
It took more than four hours to contain with help from about 10 fire trucks and two helicopters with monsoon buckets.
- Rotorua Daily Post