Investigators are probing the cause of a stubborn two-alarm blaze that damaged a North York autobody shop Thursday morning.

Firefighters were called to the building, located at 155 Norfinch Dr. near Highway 400 and Steeles Avenue West, before 6 a.m. after a TTC driver spotted the blaze.

Crews extinguished most of the flames but were ordered out of the building because of fears the weakened roof and a wall may collapse.

At least one vehicle was on fire in the shop.

Crews were also concerned about magnesium that was stored in the building because it is difficult to extinguish once it catches fire. A hazardous materials unit was sent to the scene.

No injuries have been reported.

With a report from CP24's Cam Woolley