A family of four escaped injury after a van was set on fire in the Kilbroney Road area of Newry at 5.30am on Saturday.
The blaze spread to a house, setting the porch alight. The family in the house at the time included a father, mother and two sons in their 20s. They were uninjured.
Two cars parked outside the premises where also badly damaged in the attack.
Police are investigating the incident as arson with intent to endanger life.