Firefighters worked Tuesday morning to extinguish a blaze burning an abandoned commercial building in Hillyard. One person described by fire officials as a squatter escaped from the building and said he was unsure if others were inside. Firefighters used thermal imaging equipment to check and could not find anyone else. The building, on the corner of Wellesely and Haven, has been empty for years. The windows were boarded up and homeless people have been known to gather at the one-story structure.