PITTSBURGH — Five firefighters were injured, two by falling through a roof, while battling a blaze at three buildings in a Pittsburgh neighborhood over the weekend, authorities said.

Fire crews were called just before 9:30 a.m. Saturday to the Homewood neighborhood where the fire started in one home and spread to two adjacent buildings that contained apartments.

Authorities said two firefighters fell through the roof of one of the homes while battling the flames. The roofs of at least two of the houses collapsed. All five injured firefighters were taken to hospitals with injuries said not to be life-threatening, officials said.

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Matt Brown, chief of Allegheny County Emergency Services, said fire crews were hampered by temperatures in the teens and winds up to 20 mph. The cold froze one truck’s water pumps and tanks and also froze the closest fire hydrant, and a ladder on one truck also wasn’t working properly due to the cold, he said.

At one point, firefighters used a chainsaw to cut away a second-floor wall to reach the flames inside one of the apartment buildings.

Brown said nearly 100 firefighters, many of them volunteers from surrounding communities, responded to the fire, which was declared under control at about 1 p.m. Saturday. The county fire marshal’s office will investigate the cause.