The plane, American Airlines flight 24, was preparing for takeoff to John F Kennedy Airport in New York when the security issue arose.
San Francisco Police Sergeant Michael Rodriguez said that the action was taken in response to a "verbal threat". He refused to offer further details in a brief press conference at the airport.
Passengers were led off the plane through a rear door and driven by bus back to a terminal building. One or more suspects were apparently removed through the front door of the plane.