From SF Gate

(11-21) 16:46 PST San Francisco -- Four people reporting injuries were taken to the hospital Saturday afternoon after the cable car they were riding stopped suddenly in downtown San Francisco, a Muni spokesman said.

Two passengers and the cable car's gripman and conductor sustained injuries not considered life-threatening, said Municipal Transportation Agency spokesman Judson True.

The cable car was brought to a sudden stop after a strand started to separate from the underground cable used to pull the iconic cable cars up and down San Francisco's hills at a steady 9.5 mph.

The operators were temporarily unable to release the grip from the fraying cable and radioed central control to have the system shut down automatically. No problems were reported with the other cable cars running at the time.

The incident occurred a little after 1 p.m. on the Powell Street line. The cable car was heading toward Fisherman's Wharf. Service is expected to resume Sunday morning, once the cable is repaired, True said.

Muni is running replacement bus service on Powell Street between Market and Washington streets. The other lines are not affected.