SAN DIEGO, CA - SEPTEMBER 8: Traffic is backed up after traffic lights were downt after a massive blackout hit Southern California September 8, 2011 in in San Diego, California. Approximateely 1.5 million residents from Southern Orange County to Northern Baja are without power. (Photo by Sandy Huffaker/Getty Images)
A massive power outage knocked out electricity for nearly 1.4 million customers in San Diego as well as parts of Southern Orange County, Palm Springs, and parts of Mexico Thursday.
San Diego Gas & Electric advised its customers via Twitter at 5:37 p.m.: "If you have a personal family emergency plan, please activate it now."
Capistrano Unified School District reported all schools in the district will be closed on Friday, Sept. 9, 2011 due to the power outage affecting Southern Orange and San Diego counties.
San Diego State University canceled classes tonight due to the outage. University officials said it was still unclear if classes would resume tomorrow, and updates would be posted on its website.
The California Independent System Operator (ISO), which manages the state's power grid, issued a transmission emergency notice for the San Diego area.
Late Thursday night ISO issued a news release asking Californians to conserve power Friday in an effort to "ease the strain on power, please turn off air conditioning and all major appliances to protect against power surges as power is restored to the region overnight and into tomorrow."
"It sounds like it's really widespread -- I'm hearing anyone who is a customer of San Diego Gas & Electric is affected,'' Orange County Fire Authority Capt. Marc Stone said. "It could be as widespread from Mexico to Phoenix. "
The outage was triggered after a 500-kilovolt (kV) high-voltage line from Arizona to California tripped out of service, according to the California Independent System Operator. The transmission outage cut the flow of imported power into the most southern portion of California, resulting in wide-spread outages in the region.
SDG&E said crews repaired the problem and were in the process of restarting the system but it would take several hours to actually generate power to customers.
Power was expected to be out well into the night.
"Essentially we have two connections from the rest of the world: One of from the north and one is to the east. Both connections are severed," an SDG&E official said.
San Diego City Hall was voluntarily evacuated. Some people were trapped in elevators inside, but were later freed by firefighters.
The FBI said the power outage is not related to any terror threat.
A woman who identified herself on Twitter as Lisa, Tweeted just past 6 p.m.: " At a wedding in Fallbrook, no electricity and they are delaying ceremonies hoping for power."
In the eastern Coachella Valley, a power outage knocked out electricity for an unknown number of people and businesses as temperatures soared into the triple digits.
It was not known when power would be completely restored, how many customers were affected or what caused the outage.
In Indio, the Police Department lost power for about 40 minutes and used backup generators, police spokesman Ben Guitron said.
The Riverside County Sheriff's Department temporarily handled 911 calls, and Indio police officers were sent to monitor major traffic intersections.
Orange County sheriff's deputies were responding to calls for service due to the outages in San Clemente, San Juan Capistrano, Laguna Hills, Mission Viejo and parts of Laguna Niguel, said Orange County sheriff's Lt. Jim England.
Capt. Marc Stone of the Orange County Fire Authority said the agency was urging residents to check on the elderly and their neighbors who have small children.
"Right now we're running numerous calls of people stuck on elevators," he said.
Southern California Edison said it was working with the California Independent System Operator to determine cause of the outage in the company's service territory in sections of Orange and Riverside counties.
At the San Onofre Nuclear Power Plant, two units went off line around 3:38 p.m. The shutdown was part of standard procedure during a power outage, Edison said.
The shutdown was proceeding "safely" and "poses no danger to workers or the public. Offsite power is available for the plant's safety systems," Edison said in a statement.
Meanwhile, flights into San Diego's Lindberg Field have been stopped. Gas stations and restaurants are being forced to shut down.
At one gas station in San Clemente motorists were stranded because they could not fuel up.
The San Diego border along Mexico is still open, as U.S. Customs and Border Patrol are running on back up power.
On a lighter note, Rich Cruse of Vista Tweeted: "Met the neighbors for the first time who were out on their porch. Not all is bad."