The blaze ignited around 6 a.m. on North Front Street near Callowhill Street. Video posted to the Citizen app showed the roof deck fully engulfed in bright orange flames at the height of the fire.
Fire crews responded quickly and were able to extinguish the flames within about 40 minutes. One person was treated for smoke inhalation but did not need to go to the hospital.
Carl Geiger, the building's owner, said the structure housed three luxury apartments and commercial office space, all of which sustained severe fire and water damage.
He gave Action News an exclusive look inside at the damage.
"My understanding is that it's going to take about a year to get it habitable and back to where it was," Geiger said.
Ron Spay, whose girlfriend lived in one of the apartments, said she is now looking for a new place to live.
"She is looking for another apartment and she's going to have to get all her stuff out this weekend, basically. Start fresh. It is what it is. Thank God nobody got hurt," Spay said.
In total, seven people have been displaced, not including staff from a nurse staffing agency located on the first floor.
The cause of the fire has not been officially determined. However, Geiger said he was told that "the people in there were smoking on the roof deck and left a cigarette unattended."