A three-alarm fire, probably started by a plumber's torch, caused "substantial damage" to two condominiums in Newburyport, fire officials said. Neighbors reported the fire on Congress Street at about 10:40 p.m. on Monday, Deputy Fire Chief Steve Bradbury said. No one was injured. Residents of both units in the two-story building were in Florida. The blaze probably started when a plumber in one of the units, which was being renovated, used a torch to solder pipes, Bradbury said. The fire originated in the common wall between the two side-by-side units.