City firefighters responded to the three-alarm fire, which was reported at 10:25 a.m. in the three-story Apartments at Mulberry Corners building. When firefighters arrived, the door to the woman’s third-floor apartment felt hot, said Chief Tim Gregg. The woman, whose identity was not available, was alone in the apartment, Gregg said. Firefighters helped her to exit and she was taken to the hospital, to be checked for injuries. The marshal ruled the fire was “incendiary” in nature, Gregg said. The fire was contained by the sprinkler system in the apartment building, he said. The apartment did not have extensive damage.Gregg praised the sprinkler system, saying it’s the “best fire safety device there is.” One sprinkler head was able to contain the entire fire, he noted. The Apartments at Mulberry Corners is a Housing Development Corporation building that contains 25 apartments for seniors ages 62 and older.