CHICAGO (CBS) — Two people, including a firefighter, were injured early Thursday, in a fire authorities have deemed suspicious.

Firefighters responded to a fire in the 600 block of North Springfield Avenue shortly after 2 a.m. When they arrived, they found flames on one of the side porches, and in an interior stairwell.

Crews also found a woman outside the building who had suffered minor injuries. She was taken to Mount Sinai Hospital for treatment.

A firefighter also suffered a knee injury at the scene, and also was taken to Mount Sinai for treatment.

The Fire Department said the fire started on the third floor. Police said the cause of the fire was suspicious, and the Bomb and Arson Unit was investigating.

The fire was extinguished by about 3:30 a.m. There were no smoke detectors found at the building.