"We found some indicating factors that the doors around the back of the building were open. Our submission is that someone has been in there and it was a deliberately lit or accidental fire through unauthorised occupants."
The hall was on a busy stretch of State Highway 2 and Mr Rackham said it was likely people driving past between 5.30-6pm had noticed unusual behaviour.
"It was an unused hall and maybe someone driving past noticed a car there when it's normally empty.
"If anyone saw any vehicles leaving the area or anybody on foot in the vicinity, we encourage them to contact Tauranga police."
Mr Rackham said firefighters had been at the scene until about 1am yesterday and were again called about 6am after concerns that it may have reignited. "The structure was quite dangerous and the remaining walls made it quite difficult for the firefighters to access some of the area safely."
Western Bay District Council group manager of engineering services Gary Allis said there had been cases of vandalism over the eight years the hall had been vacant, mostly involving broken windows, but there had been no known cases of squatters. "We've kept an eye on it, we've had people mowing the grass and things."
He said asbestos had been found in the building yesterday, which needed to be treated "in the proper manner," before it was demolished in the afternoon.Mr Allis said the building had been going through processes to be put on the market early next year.
The building and land were offered back for sale to the McNaughton family, which gifted land the Tauranga County Council in 1930, but the family decided not to go through with the purchase.
The plan was then to sell the property on the open market as a lifestyle or residential block but before that could happen regulations required that an entrance to the state highway was up to standard.