Three deliberate fires were put out by firefighters from Illingworth Fire Station over night.
The roofs of two adjoining empty houses were set ablaze at around 9.45pm yesterday evening.
Fire investigators believe that somebody had broken in and set fire to the first floor of the house.
There was also a bin fire in the same area.
Another fire was started outside a house in Boothtown at around 2am this morning.
Rubbish outside the property was set on fire, causing the side of the house to blacken and pipes to melt.
This led to the house on Gordon Street being filled with smoke.
It is not clear whether the incidents are linked.