In the first incident, a car was extensively damaged when it went on fire in the driveway of a Taieri Rd, Dunedin, house about 1.30am.
Fire safety officer Barry Gibson said it appeared the fire was deliberately lit and police were investigating.
A second suspicious fire, about 6am, gutted a vacant house in Dolphin St, Northeast Valley.
The Fire Service was working with police after an initial investigation found the fire was most likely deliberately lit, in the area around the back door, Mr Gibson said.
The owner of the building, who is out of town, had yet to be spoken to last night.
At 8.30am yesterday, the Outram fire brigade was called to a house fire in Bidston St, Outram.
Chief Fire Officer Barry Barbour said the fire appeared to have started in rubbish at the back door of the house and had spread into the roof by the time the brigade arrived.
"A few minutes later and it could have been quite interesting."
Two women inside the house were unaware of the fire until a passer-by knocked on the door and told them to get out, Mr Barbour said.
The house was damaged on the outside, with some minor damage in the kitchen.
In the final incident, a 33-year-old man was treated at the scene for superficial burns to his hands and face, after he set a car on fire while drilling a hole in its fuel tank at an Elmwood Dr house in Mosgiel, about 11am.
Senior Sergeant Mel Aitken, of Dunedin, said the car belonged to the man, who was in the process of stripping it.
The Mosgiel fire brigade put out the fire, which caused extensive damage to the car and a nearby garage.
