San Diego Gas & Electric said it had restored power to most of its 1.4 million customers by 3:25 a.m. Sept. 9 after a major blackout nearly 12 hours earlier hit San Diego County along with areas of Orange County and parts of Mexico.

The company, which is a subsidiary of San Diego-based Sempra Energy, said it coordinated restoration efforts with the California Independent System Operator Corp., the entity that controls the state’s power grid. Power was restored sooner than expected. SDG&E initially said restoring power could take till later in the day Sept. 9.

While traffic jams ensued immediately after the outage on regional highways and surface streets and Lindbergh Field had to shut down outgoing flights, civil order remained in place thanks to rapid response from the San Diego Police Department.

SDG&E initially said the origin of the blackout came from a severing of a power line in western Arizona, but it has yet to officially state the reason why the power outage was so widespread.

“SDG&E and the ISO are focusing their efforts over the next few days on maintaining and ensuring the integrity of the local power system,” according to a company statement. “Upon meeting that goal, the company will turn its attention toward determining the sequence of events that led to the outage and establishing practices and procedures to ensure that outages such as the Sept. 8 event are not repeated.”

According to The Associated Press, the outage was likely caused by an employee removing a piece of monitoring equipment at a substation in Arizona. The power loss should have been confined to the Yuma, Ariz., area, but quickly led to a systemwide failure.

Two nuclear power reactors at San Onofre automatically went offline Sept. 8 as the plants are programmed to do in the case of a disturbance in the power grid, said the AP story.

An initial estimate of the economic losses attributed to the blackout was $97 million to $118 million, according to the National University System Institute for Policy Research. The research organization said the bulk of the estimated loss, about $70 million, came from productivity losses, followed by $10 million to $20 million in overtime payments to government employees.

— Mike Allen