A fire in a three-story apartment building Sunday injured five San Francisco firefighters and at least one tenant, and left 37 people homeless, officials said. The cause of the four-alarm blaze in the city\'s Mission District had not been determined, KCBS Radio reported. The fire was reported at 9:49 a.m. and was contained by 1:15 p.m. The firefighters were hurt when a staircase collapsed inside the apartment building. KCBS said their injuries were not considered life-threatening. The radio station said one tenant also was injured, while the San Francisco Chronicle said four residents were hurt. The building also housed a liquor store on the ground floor. A second building also was scorched by the flames, firefighters said.