San Francisco police are investigating the death of a man whose body was found inside a city bus that had been parked in a transit yard for hours after a rush-hour shift.

Authorities say a cleaning crew discovered the body of 37-year-old Christopher Feasel of San Francisco over the weekend. They are trying to determine whether he went unnoticed by passengers or the driver or if he broke into the yard and died in the parked bus.

Drivers are supposed to check vehicles at the end of their shifts.

Police Sgt. Lyn Tomioka says investigators will check surveillance video around the bus yard. It's not clear whether cameras on the bus were working.