A Nigerian worker was crushed to death when he was pinned in the doorway of an elevator in the basement of the Transamerica pyramid building, police said. Washington B. Olaye, 32, was attempting to pull a mail cart into the elevator Wednesday morning when ``for no apparent reason'' the elevator began moving up, said police Officer Sherman Ackerson. A co-worker, identified as Isiah Sampson, was inside holding the doors open for Olaye, Ackerson said. Both workers were heading to the 18th floor to Montgomery Securities, where they worked. Olaye, standing on the elevator's threshhold, was pinned between the elevator and the roof of the basement floor, Ackerson said. Fire Department personnel arrived and pried the door open, but Olaye, who lived in nearby Oakland, was pronounced dead at the scene by paramedics. An investigation was being conducted by federal and state worker safety officials and the Otis Elevator Co., the manufacturer. Elevators are not supposed to operate when the doors are open.