A BART technician accidentally entered an emergency-scenario computer command Wednesday morning, shutting off power to the entire transit system for about 20 minutes and creating residual delays on every train and every direction for the next hour.

The power failed at 10:24 a.m., causing trains to go into manual mode as transit officials worked to restore the automatic train control system, said Taylor Huckaby, a BART spokesman. The command the technician inadvertantly hit is usually only used during emergency trainings, he added.