The blaze in Crumpets Farm Drive, Lytchett Matravers, started at about 11:00 GMT.
Acetylene cylinders were believed to be inside the property and a 70m (230ft) cordon was put in place.
Dorset Fire Service said the A350, which was partially closed, had now reopened. An investigation has started.
Residents whose properties were not affected returned home at 18:00.
Fifteen residents, including a baby, were evacuated from their homes after a fire broke out in a nearby garage in Dorset.