Police are investigating two blazes in mid-Northland: one in which petrol was lit in a Kaikohe flat, the other the destruction of Rawene's historic school hall.
The Kaikohe fire was five days after the Rawene hall went up in flames. Both are being treated as suspicious.
Kaikohe Constable Daniel Cleaver said it was fortunate a woman and her adult daughter were not home at the Rankin St flat when the fire broke out around 4pm on Friday.
The flames spread through the roof to two neighbouring units, causing smoke and water damage. Those units were also believed to have been unoccupied at the time.
Mr Cleaver said a neighbour noticed the fire after smoke alarms in the flat went off.
Police have strong leads as to who lit the fire but no one has yet been arrested.
The mother and daughter are staying with relatives in Kaikohe.
Meanwhile, the destruction of the 147-year-old Rawene School hall is being called suspicious because police have not been able to find a cause.
Northland fire safety officer Lindsay Murray said the fire began inside the Marmon St hall in a storage area. Nearby gymnasium pads caught alight, helping fuel the blaze.
"There's nothing really there to have caused the fire," Mr Murray said.
Broken windows at the back of the hall, which had been smashed before the fire, could have provided easy access inside, but Kaikohe police Detective Pete Hayes said there was nothing to suggest that anybody had entered the building.
No one had come forward with information on the fire, which had threatened a nearby home.
Rawene School principal Para Meha expects the remains of the hall to be bulldozed this week. The school's board of trustees wants to build a replacement, but the Ministry of Education will have the final say on who pays.
Mr Meha said if the hall was rebuilt, he wasn't sure whether it would be on the same site or up the hill where the school was.
The hall was originally part of Rawene District High School, which was destroyed by fire in 1972. The hall and another building were the only survivors.
The school was rebuilt further up the hill after the fire, but only for primary school pupils.