The crash occurred around 8:50 a.m. when a 12-Folsom line bus leaving the Muni terminal turned from Howard Street onto Embarcadero and collided with another vehicle, said Muni spokesman Judson True.
A pedestrian was struck during the crash, according to True.
"The coach and automobile had a collision that resulted in a further collision with a pedestrian," True said.
The pedestrian was transported to San Francisco General Hospital but the extent of injuries was unknown, according to True.
The Muni bus involved in the crash was taken out of service for the day. No other lines or buses on the 12-Folsom line were affected by the crash, according to True.
The driver of the Muni bus will undergo drug testing and be placed on leave in compliance with routine administrative procedure following a crash.