Fire late Sunday night forced several tenants to flee their homes on Liberty Street in Butler, authorities said.
No one was injured but at least four people were left homeless. A pet dog also died in the fire about 10:20 p.m.
The state police fire marshal has been called to investigate; however, the blaze was not immediately considered suspicious, fire officials said.
The Butler Fire Department was called to the home at 328 Liberty St., where firefighters found flames and smoke coming from the back of the three-story house.
The house is divided into four apartments. All the units were believed to be leased but it was not immediately known how many people lived there and how many were home at the time of the fire.
Firefighters quickly extinguished the blaze but not before all the apartments sustained fire, smoke and/or water damage.
Butler police, who assisted at the scene, identified the owners as David and Kathy Bazzone, who could not be reached for comment. A damage estimate was not available.
The Butler chapter of the American Red Cross also was called to help the tenants with emergency needs including temporary housing.