A six-alarm fire that probably began in the basement of a large apartment building near Central Square early on Thursday morning displaced about 25 residents and injured two firefighters, according to city officials. The fire at 884 and 888 Massachusetts Ave., which began after midnight, traveled up the six-story building through utility chases, climbing inside the walls and ceilings, said Deputy Fire Chief Lester Bokuniewicz, but firefighters were able to contain it to the right side of the building. No residents were injured, and the firefighters were treated and released, he said.Catalina Gaitan contributed to this story. She can be reached at email@example.com. Follow her on Twitter at @catalina_gaitan. Evan Allen can be reached at firstname.lastname@example.org. Follow her on Twitter @evanmallen.