The Fort Wayne Fire Department residents in three of the five apartments were home at the time, but all got out safely. One cat is believed to have gone missing since the fire.
The former owners of the home tell WFFT the building is 134 years old -- something firefighters say made it harder to get under control. Crews were on the scene into the early evening on Sunday.
"This is a brick structure, it has a slate roof," says Stacy Flemming, a fire department spokeswoman. "Take that, and then you have a fire inside and the heat and the energy is very strong. It's not the typical fire that would vent out of the roof. It's actually being held in."
Officials say the inside is severely damaged, but the owner tells WFFT that he plans to restore the building. No word on what caused the fire.