Emergency crews were called at 10:26 a.m. Wednesday to 305 South Street where flames were making their way through Lorenzo and Sons Pizza Inc. on the first floor and an apartment on the second floor.
Officials say one firefighter was treated and released at Hahnemann Hospital after sustaining a knee injury.
The fire department is continuing to work to get the fire under control.
There is still no word on what may have sparked the blaze.