Firefighters with the Pittsburgh Bureau of Fire responded to a 3-alarm commercial structure in the 900 block of Wood Street in Wilkinsburg just after 2 a.m.
A male was transported to the hospital in critical condition with burn injuries by Eastern Ambulance.
No firefighters were injured. Ten other residents from upper level apartments safely evacuated the structure.
The fire was declared under control about an hour into the response.
The cause will be investigated by the Allegheny County Fire Marshal.
Tonight, the City-County Building is illuminated to recognize Poison Prevention Week and the 50th Anniversary of "Mr. Yuk" in partnership with Children's Hospital of Pittsburgh of UPMC.
For questions about the lighting at the City-County Building, please reach out to the Office of the Mayor.