The burning container vehicle was reported near the main Lurgan turn-off just after 6.30pm.
Police said the road was closed between junctions 9 and 10. Diversions were put in place at Moira and Lough Road.
Northern Ireland Fire and Rescue Service crew have brought the fire under control and remained at the scene on Wednesday night.
A NIFRS spokesperson said the driver had a "lucky escape" after the fire rapidly engulfed the vehicle, which was transporting timber goods.
The motorway was expected to remain closed in both directions until the early hours of Thursday morning.