Power outage affects five million people in California, Arizona and Mexico.
Power has been restored to 1.4 million customers as the system recovers from a major outage that affected a wide area of Southern California.
The outage was accidentally triggered at about 4 p.m. Thursday when an electrical worker removed a piece of monitoring equipment at a power substation in southwest Arizona.
The outage extended into southern Orange County, across California's inland deserts, as far east as Yuma, Ariz., and into Mexico. The region is home to some 6 million people.
The outage left residents and businesses without air conditioning and caused major backups for motorists. Power was restored to different parts of the region throughout the ovenight.
Commuters also faced a shutdown of the trolley system that shuttles thousands of commuters every day in San Diego. Trains were stopped in Los Angeles, an Amtrak spokesman said, because there was no power to run the lights, gates, bells and traffic control signals.