CFD said the bus was trying to go from the Randolph Street exit of DuSable Lake Shore Drive to lower Randolph Street.
That's when the Big Bus Tours vehicle struck the support beam that holds DuSable Lake Shore Drive because it was too tall to clear it, CFD said.
CFD said one adult was taken to Northwestern Hospital in serious condition. Thirty-one other people refused treatment on the scene.
Police have not said if any citations will be issued.
Further information was not immediately available.
This is a developing story. Check back with ABC7 for updates.