However, the fire investigator's report, released under the Official Information Act, concludes the physical evidence conflicts with the statements of a man and woman who admitted lighting a fire in the building.
The category 2-listed homestead, which was occupied by runholders of the former Mt Aurum Station from the 1890s until 1969, burned to the ground about an hour after campers first noticed flames just after 2am.
The report's author, Stuart Ide, said the fire started in a bedroom, which had an open fireplace but a sealed-off chimney.
The man and woman - who did not come forward until the next day - told police they lit a fire in the fireplace but claimed to have later doused it with water.
The report said it was unknown how big the fire was or how long it had been allowed to burn, although a camper had seen a glow from a fire in the bedroom about 10pm.
Mr Ide said the ``evidence as presented does not match the statements of the last two people in the building''.
A lack of charcoal in the grate indicated the fire may not have been lit there, or that embers were removed.
A high reading for an accelerant on an underfloor pile beneath a corner of the homestead's bedroom could not be explained, he said.
Neither the police nor the Department of Conservation have laid charges.
When other campers noticed the homestead was on fire about 2am, the pair had already left the camp site.
Thanks to campers' efforts, the fire was contained to the homestead and a small outbuilding.
The building was restored in the 1990s, and further restoration work was carried out in 2011.
The building's fireplaces were not functional, which was advised by a sign in the homestead.
