APS launches probe into massive power outage

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YUMA, AZ (CBS5/AP) -

Arizona Public Service Co. says it has launched an investigation to determine what triggered a massive power outage that hit Arizona, Southern California and parts of Mexico.

APS spokesman Damon Gross tells The Associated Press they will look for reasons why work an employee was performing yesterday in a substation near Yuma became so widespread an issue.

Gross says the worker was doing some preventative maintenance work on a piece of equipment called a capacitor when it triggered the massive power outage.

Crews have restored power to most areas of California, Arizona and Mexico, as the power company that caused the outage tries to figure out how it happened.

Electricity was restored in San Diego to all of San Diego Gas & Electric Co.'s 1.4 million household and business customers -- the biggest block of people affected.

Mexico's electrical utility says the lights are also on for about 1.1 million customers, or about 97 percent of those who lost power. A few industrial clients were still without it.

Power was also restored to all 56,000 customers in Yuma, Ariz.

The California utility made the announcement a day after a large swath of the Southwest and parts of Mexico lost electricity, and restoration of power came sooner than expected.

Most of the people affected were San Diego Gas & Electric customers.

The blackout also caused a 3.2-million gallon sewage spill that has closed some San Diego-area beaches. All public schools in the city also are closed Friday as well as local state universities and community colleges.

An Arizona Public Service employee removing a piece of monitoring equipment that was causing problems likely caused the massive outage that left more than 2 million people without electricity about 4 p.m. Thursday.

"Operating and protection protocols typically would have isolated the resulting outage to the Yuma area," APS said in a statement Thursday night.

"The reason that did not occur in this case will be the focal point of the investigation into the event, which already is under way," the statement read. The outage should have been limited to the Yuma area, authorities said.

The North Gila - Hassayampa 500 kV transmission line near Yuma tripped offline, resulting in the outage, APS said. Among APS customers, at least 56,000 lost service throughout Yuma, Somerton, San Luis and Gadsden.

It did not impact anybody in the Phoenix area.

The San Diego area was hit especially hard with power severed to all of San Diego Gas & Electric Co.'s 1.4 million household and business customers, the company said.

The outage extended into southern Orange County, across California's inland deserts, as far east as Yuma, Ariz., and into Mexico.

Public schools in San Diego County and parts of southern Orange County will be closed Friday as a precaution as area residents cope with a power outage that has left millions without electricity.

School officials announced closures of schools in the Capistrano Unified School District and the San Diego Unified School District.

San Diego schools superintendent Bill Kowba said in a news conference Thursday that the closure will affect 200 campuses.

Officials say they are erring on the side of caution but expect schools to be operating normally Monday.

Capistrano schools superintendent Joe Farley says it's unclear what will happen to Friday night sporting events.

Dan Froetscher, an APS vice president, would not say how much experience the employee had.

APS said late Thursday night that  electricity has been restored to everyone in Yuma.  APS officials say the outage affected its customers in Yuma, Somerton, San Luis and Gadsden.

Thursday's high in Yuma was 113 degrees.

Some flights at Yuma International Airport were canceled Thursday night because of the power outage.

Arizona Western College and NAU-Yuma already have canceled classes for Friday. So have the Yuma Union High School District, Yuma Elementary District 1, Crane Elementary District and the Amerischools Academy campuses.

Public schools in San Diego County and parts of southern Orange County will be closed Friday as a precaution as area residents cope with the power outage.

School officials announced closures of schools in the Capistrano Unified School District and the San Diego Unified School District.

San Diego schools superintendent Bill Kowba said in a news conference Thursday that the closure will affect 200 campuses.

Officials say they are erring on the side of caution but expect schools to be operating normally Monday.

Capistrano schools superintendent Joe Farley says it's unclear what will happen to Friday night sporting events.

The utility is warning California customers that power could be out through the night and into Friday.

All outgoing flights from San Diego's Lindbergh Field have been halted.

Officials at Sky Harbor International Airport in Phoenix say so far one flight into San Diego has been delayed.

The San Onofre nuclear power plant in Southern California has shut down because of the outage. Charles Coleman, a spokesman for Southern California Edison, said that the plant went offline at 3:38 p.m. Pacific as it is supposed to do when there is an electrical disturbance.

Coleman says there is no danger to any residents or employees at the plant, but it is not currently generating power.

The larger outage is affecting 500 to 2,000 SoCal Edison customers in southern Orange County and Riverside County.

Orange County sheriff's spokesman John McDonald says deputies have been dispatched to major intersections to direct traffic because traffic signals are out. There have also been reports of people stuck in elevators.

Thirteen police stations in San Diego County were without power but were able to continue operating and taking 911 calls by using generators, said police spokeswoman Andra Brown.

Stay with KPHO.com and CBS 5 News for updates.

Copyright 2011 KPHO. All rights reserved. The Associated Press contributed to this report.