Six fire appliances were called out after receiving reports of a fire near the small village of Stuartfield south-west of Mintlaw.
The fire service was dispatched after receiving a call that a fire had erupted at a house at around 9.45pm on Saturday, June 18.
About 30 crew members were on the scene at 10pm to battle the blaze which had engulfed a house and a vehicle parked outside.
The property was located just outside Stuartfield and the fire service confirmed there was no risk of it spreading to nearby buildings.
Crews battled the blaze for several hours before dispatchers received the stop message just before 2am on June 19.
They remained on the scene until 5.30am as a precaution.
A fire service spokeswoman says that “the incident has been left with the police” and is being treated as suspicious.
A police spokeswoman said: “Officers attended at Stuartfield at around 10.15pm on Saturday, June 18 following reports of a fire.
“A vehicle and a derelict property were found alight. There were no reports of any injuries.
“A joint investigation is to be carried out with Scottish Fire and Rescue Service to establish the cause of the fire, which is being treated as suspicious.”