Businesses on Bay and River streets are being evacuated after the explosion at 8:45 a.m. Monday that police said blew off three manhole covers.
Georgia Power spokesman Swann Seiler said the explosion happened near Abercorn and Bay streets.
Firefighters sprayed foam and water at the scene, and the fire was out by 10 a.m. Some power outages were reported.
Police were urging morning commuters to avoid the area and seek alternate routes.