The Norwell Fire Department is investigating a fire of suspicious origin at 57 Washington St. that 20 firefighters from Norwell, Hingham, and Rockland contained after arriving at the scene at 11:20 p.m on July 14. Twenty percent of the unoccupied building was damaged but no civilians or firefighters were injured, according to Norwell Fire Chief Andrew Reardon. “It appears the fire started at the exterior rear of the building and worked its way inward. I am considering the fire to be intentional,” he said. Reardon said the building, formerly the location of the New England Real Estate Journal, is not a known hangout for transients despite sitting empty for about a year. Firefighters were perplexed about the source of the blaze because the building’s utilities are disconnected, and weather, such as lightning, was not a factor, Reardon said. Hanover firefighters were called in to staff Norwell’s fire station during the emergency.