Residents were evacuated from their homes on Thursday after cylinders were discovered in the blaze off Ashley Road in Parkstone, Poole.
Roads have been re-opened and residents have been allowed to return home.
But firefighters suspect the roof contained asbestos. They said the risk was small, but people who see white deposits should close their windows.
Dorset Fire and Rescue Service was called to the fire in a vehicle body repair shop early on Thursday afternoon.
Nine fire engines and 65 firefighters were sent to the address. There were no reports of injuries.
Minimal risk
Dorset Fire Service Said the Health Protection Agency advised any risk from asbestos would be minimal, but there were a number of precautions people should follow if they see whitish material or flakes.
Dorset fire said residents should not touch, break or crush it as this may release asbestos fibres.
If there are deposits, people should keep their windows and doors closed and wear gloves and a damp cloth to wipe window sills, not a brush, dry cloth or vacuum cleaner.
The cloth and gloves should be sealed in a plastic bag and left outside.
Dorset fire service said residents should warn children not to play with the material.
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