An investigation is underway after residents were evacuated from an apartment building in Downtown Pittsburgh for a reported fire. Pittsburgh Bureau of Fire was called to the Midtown Towers at 643 Liberty Ave. just after 6:45 p.m. Tuesday after reports of a fire from inside the building. When officials arrived on the scene, smoke was seen coming from the apartment on the 13th floor. Firefighters were able to quickly put out the fire, which was contained to one unit in the building. Officials said all residents have since been allowed back into an apartment building. Tenants who were affected by the fire have been offered temporary accommodations within the building. The Fire Investigation Unit is looking into the cause of the fire.