Mayor Ed Lee and other city officials were on the new bus waiting to be taken to City Hall after a news conference at Pier 48 near AT&T Park when the mishap occurred.
The bus could not be driven away, and the mayor and the rest of the group had to be ushered onto another bus. Muni spokesman Paul Rose said it appears there was an issue with the bus' hydraulic system.
The vehicles are part of a fleet of 62 new biodiesel-electric hybrid buses being introduced into the Muni system, which has not had any new buses since 2007, agency officials said.
