Three SA fires thought suspicious

Two cars, a truck and a house have all been damaged in fires in South Australia, with police declaring the three incidents suspicious.

In the first on Tuesday night two cars were destroyed and minor damage was caused to a carport at a property at Goolwa North, south of Adelaide.

Just before 1.30am on Wednesday about $150,000 damage was caused to an unoccupied house at Alberton, in Adelaide's north-western suburbs, while a truck was destroyed in a fire at a business at suburban Burton soon after.

Police believe all three fires were deliberately lit and investigations are underway.