Eight vehicles were set alight outside a house in south Armagh on Monday morning.
The fire had also spread to the house which is situated on the Carrowbane Road in Belleeks.
Firefighters battled through the night to contain the blaze which was reported shortly after 1.30am.
Five crews – two from Newry, two from Newtownhamilton and one from Warrenpoint – attended the scene
The road, between the junctions with Tullyah and Kesh Road, remains closed this morning.
A NIFRS spokesperson said: “Firefighters wearing breathing apparatus used six jets to extinguish the fire. The incident was dealt with by 4.40am and the cause of the fire is believed to be deliberate ignition.
Detectives in Newry are appealing for information and witnesses to come forward.
Detective Sergeant McCarragher said: “Police received a report at approximately 1.45am that a number of vehicles were alight at the Carrowbane Road, Belleek, just outside Camlough. Colleagues from the Northern Ireland Fire and Rescue Service attended along with the Ambulance Service. Eight vehicles were extensively damaged.
“One van that was parked close to the front outer wall of the property was also set alight resulting in the spread of fire to the house. Thankfully no-one was present in the property. We are treating this incident as arson with intent to endanger life.”
“The Carrowbane Road remains closed at this time due to icy conditions.
“Our enquiries are continuing and we would appeal to anyone who was in the area at the time of the incident or who may have CCTV footage to contact us on 101 quoting reference number 86 17/01/22.”
A report can also be made using the online reporting form via www.psni.police.uk/makeareport
Alternatively, information can be provided to Crimestoppers anonymously on 0800 555 111 or online at www.crimestoppers-uk.org