A fire at a Chevron refinery just north of San Francisco on Monday has prompted emergency evacuations and orders for nearby residents to remain indoors as firefighters grappled with 20 meter high flames. The fire at the refinery in Richmond, California began at 5:24 a.m. local time, and its cause remains unknown, according to local government Hazardous Materials specialist Maria Duazo The local KGO television channel reported that workers were being evacuated, while toll operators at the nearby Richmond-San Rafael bridge were removed due to health concerns. Police and emergency workers reportedly ordered residents to stay indoors, close their doors and windows and shut off ventilation. A Chevron spokesman was not immediately available for comment.