Five people were injured Wednesday when a San Francisco cable car came to a sudden stop in the city's Nob Hill neighborhood, authorities said.
One of the injuries — an elderly man who fell and hit his head — was considered life-threatening, San Francisco Fire Department spokeswoman Mindy Talmadge said.
Four other people were taken to a hospital with non-life-threatening injuries.
The Muni cable car had about 50 passengers onboard.
San Francisco Municipal Transportation Agency Director John Haley told reporters at the scene that it appeared a 1.5-inch bolt stuck in the cable car's track caused the sudden stop.
Additional details were not immediately available.