Power company employee caused massive blackout, utility says

An Arizona power company said Thursday that a worker probably caused the power outage that left large parts of Southern California and the surrounding region in the dark.

APS, which is Arizona’s largest electric utility said a power line was tripped near Yuma, Ariz., at 3:30 p.m. Thursday during maintenance work.

 PHOTOS: Blackout leaves millions without power

"The outage appears to be related to a procedure an APS employee was carrying out in the North Gila substation, which is located northeast of Yuma," an APS press release said. "Operating and protection protocols typically would have isolated the resulting outage to the Yuma area. The reason that did not occur in this case will be the focal point of the investigation into the event, which already is underway."

San Diego Gas & Electric said it is attempting to begin restoring power in some areas. But they said the outage might last into Friday evening in some areas.

More than 1.4 million people in a large swath of Southern California and beyond were affected as a blackout brought normal life to a halt.

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Photo: Closed pumps are taped off at a gas station in Encinitas, Calif., after a blackout Thursday in San Diego County. Credit: Dennis Poroy/Associated Press