Firefighters have extinguished a truck fire on the Barton Highway north of Canberra this morning.

Just after 6.30am, ACT and NSW Emergency Services responded to reports of a truck on fire on the Barton Highway just south of Nanima Road.

Firefighters arrived to find the bottom of the trailer well alight, the cab of the truck had disconnected prior to their arrival.

Two ACT Fire and Rescue Compressed Air Foam trucks, two ACT Fire and Rescue Pumpers, two trucks from NSW Rural Fire Service, a truck from Fire Rescue NSW and an ACT Fire and Rescue commander attended the scene.

Firefighters used foam to suppress and extinguish the fire that started on a trailer believed to be carrying Potash. 

The cause of the fire is believed to be from a mechanical fault.

The road was closed for a short time.

NSW Police were also in attendance.