Around 300 cars were set alight at a scrapyard in Keady during the early hours of this morning.
Firefighters tackled the blaze on Madden Road for several hours from 2am, before finally extinguishing it at 9.35am this morning.
PSNI were also at the scene and advised residents in nearby houses to keep doors and windows closed due to the smoke.
Fire crews from Armagh, Keady, Newtownhamilton, Warrenpoint, Portadown, Banbridge, and Newry attended throughout the course of the incident.
They were joined by a Command Support Unit from Lisburn and Fire Emergency Support Service.
One local resident contacted Armagh I to say how the noise from the quarry stirred her whole house.
She said: “We were woke by loud explosions before 2am. We weren’t 100% sure what or where it was but a number of fire engines raced past. There was a lot of thick black smoke.”
The incident is being treated as a deliberate act.