Pittsburgh Firefighters responded to a 911 report of a structure fire around 11:30 a.m. on the 500 block of Alpine Avenue.
Arriving crews found flames and heavy smoke coming out of a third-floor window. It took about 20 minutes for firefighters to knock down the 2-alarm fire.
No injuries were reported. At least one residence is uninhabitable, with significant damage at the second and third floors.
The Fire Investigation Unit, which is comprised of Pittsburgh Fire investigators and Pittsburgh Police detectives, is investigating the cause of the fire.