The conductor, gripman and two passengers on the cable car were injured when service was suddenly disrupted on the Powell Street portion of the Powell-Hyde historic cable car line at 1:08 p.m., according to Muni spokesman Judson True.
The injuries are not believed to be life threatening, True said.
A strand on the cable must be repaired, he said. The cable is composed of strands of smaller steel wires wrapped around a rope core.
Cable car service on Powell Street will be suspended until the start of regular service Sunday morning, according to True. During the service disruption, Muni is running buses on Powell Street between Market and Washington streets to serve passengers.
The line runs between Fisherman's Wharf and the cable car turnaround at Powell and Market streets.