It broke out at 6:30 a.m.at the Neatsfoot Oil Refineries Corporation in the 2900 block of East Ontario Street.
Fire officials say a gas boiler caught fire on the second floor, sending flames shooting up through a chimney.
The flames were visible to firefighters arriving on the scene.
Crews were able to contain the fire to the boiler room. It was declared under control in less than half an hour.
No one was injured.
Investigators are still working to determine what sparked the blaze.