The Cedar Rapids Fire Department responded to a fire on the 4300 block of 1st Avenue West at 3:03 p.m. Monday.
When crews arrived they found black smoke coming from a lower unit in the apartment complex.
Firefighters responding were delayed while driving due to a natural gas line that was hit and leaking a few blocks away so the closest engine companies were on that call when the fire call came in.
Residents said everyone was out of the unit on fire and the unities on each side and above it.
Crews were able to knock down the fire after entering the apartment and began removing ceiling and wall material checking for extension.
Another engine company pulled a second line to extinguish the fire on the outside of the building.
The fire didn't spread to other units of the building, but the surrounding units did have smoke damage.
The unit that was on fire has major fire, heat, and smoke damage.
Cedar Rapids police, the American Red Cross, and Area Ambulance Service assisted at the scene.
The cause of the fire is still under investigation.