Updated at 5:35 a.m Friday. Keep refreshing this page for new information.

San Diego Gas & Electric Co. said Friday it restored power at 3:25 a.m. to its 1.4 million customers affected by the massive regional outage—far sooner than expected.

In a news release (attached), the utility said: "The restoration was accomplished almost exactly 12 hours after a major electric transmission system outage in western Arizona and the loss of a key connection with the San Onofre Nuclear Generating Station and other factors resulted in the most widespread power outage in the company’s history."

"Restoring power in the aftermath of the loss of the entire local grid serving San Diego and southern Orange counties was a monumental task and the Cal-ISO, the region’s power plant managers and our employees really rose to the challenge," said David Geier, vice president of electric operations.

"The restoration process, however, has left our local power grid very fragile and we are asking our customers to conserve electricity throughout the day Friday."

SDG&E and the Cal-ISO said they are focusing their efforts over the next few days on maintaining and ensuring the integrity of the local power system. 

"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."

But isolated outages may persist, and the company said customers experiencing an interruption in electric service should all SDG&E at 1-800-411-SDGE (7343). San Diego County officials said the precautionary boil water order was still in effect for the communities impacted by the power outages at the City of San Diego pump stations.

SDG&E President Mike Niggli confirmed that the power outage was triggered by an Arizona employee.

The announcement, made at a 10 p.m. press conference Thursday, came after Arizona Public Service said one of its employees was carrying out a "procedure" in a substation northeast of Yuma that led to the biggest blackout in county history.

"It was a very solid short-circuit that was carrying a lot of power," Niggli said.

He said power was coming back in different areas of the county as substations returned to the grid after the massive blackout hit the region around 3:40 p.m. Thursday on one of the hottest days of the year. 

Customers from south Orange County to Arizona and Tijuana were affected in the "unprecedented" outage, which snarled freeways, halted phone and trolley service and knocked radio stations off the air. Camp Pendleton lost power, reported KOGO AM 600. Hospitals including Rady Children's were operating on backup generators.

"This is an event that has never occurred in San Diego," Niggli told KOGO radio at 6:15 p.m. "We're starting to get pieces [of the grid] back. ... Thank you for your patience."

"We want everybody to be safe," said an SDG&E speaker at an 8 p.m. news conference from the county emergency operations center.  "We have deployed all our crews into the field to switch the circuits back on. Again, slow process. It's going to take a while. But the system restoration has started."

Sheriff Bill Gore said: "Stay off the roads; the gas stations aren't working. Stay at home and listen to radio transmissions [on KOGO]. Try to keep the cell phone lines open [for emergency responders]."

All public and Catholic schools will be closed Friday, officials said. Most private schools will be shut.

"We want to keep all our children safe," said the county schools chief. "Caution parents on use of candles tonight, and potentially tomorrow."

MTS buses will run Friday and county courthouses will open, officials said.

A "boil-water" order was issued for Scripps-Miramar, Tierrasanta, San Carlos, Bernardo Heights, Scripps Ranch, La Jolla-Soledad, Otay Mesa and the College Grove area, Adrian Collins, a spokesman for San Diego's water department, told The San Diego Union-Tribune.

"Reduced water pressure in those areas was caused by the lack of backup generators at eight of the 49 water pump stations around the city," Collins told the paper.

A Ramona Municipal Water District spokesman told KOGO: "It's very important for people in our district to conserve water. ... We can't pump water up the hill when we don't have electricity."

Ramona water officials asked SDG&E for a generator for the Poway pump station. Ramona has already sent its own smaller backup generators to Country Estates, Mount Woodson and downtown Ramona. 

A Helix Water District spokesman told KOGO that the County Water Authority has declared an emergency—asking Helix customers to use only indoor water.

He said customers in La Mesa, El Cajon, Spring Valley, Lakeside and other affected areas must use no outside water and that a customer in the Grossmont College area was reporting no water to his home.

Officials said Fallbrook Public Utilities, Valley Center Municipal Water District and the city of Coronado also are asking for extraordinary water use only—indoor water only.

SDG&E's Niggli said the 500,000-watt central Arizona transmission line that triggered the wide outage was restored to service, but that two units of the San Onofre nuclear plant automatically shut down.

A spokeswoman for the county Office of Emergency Services told KOGO radio that it was a "level 3" emergency.

"Please be aware that the FBI does not have any information that indicates the power outage is related to any act of terrorism," said Special Agent Darrell Foxworth.

Niggli told KOGO that power would be restored for some parts of the county Thursday night but that "pockets" would go without service well into Friday after a "large switching station" in Arizona was knocked out.

A "cascading event" overwhelmed the system, leading to "too many outages in too many places," said a spokesman at SDG&E headquarters. 

The Escondido and Otay Mesa power plants were to be brought online first, "working from the inside out," the utility said.

"This was a fairly severe event," SDG&E said at its Kearny Mesa base. This could be an extended outage, the spokesman said. 

"Just chill out while the power is out," he said. He urged people to turn their air conditioning and other major appliances off in anticipation of the power being restored.

The Sheriff's Department Operations Center in Kearny Mesa was activated, and its 911 Communication Center is on backup power, said spokeswoman Melissa Aquino.

"Please advise the public to only call 911 if it's an emergency," Aquino said. "Sheriff's deputies are out on the streets conducting traffic control and community security.

"They are receiving a lot of home alarm calls because of the power outage. Please be informed that deputies will not be able to respond to nonemergency calls until further notice. Detention facilities are operating under normal conditions, but public visits have been suspended."

The county added: "Residents without power can get information from KOGO AM 600 and other local radio stations."

SDG&E said it would post updates on Twitter at twitter.com/sdge

The county Office of Emergency Services told KOGO radio—a designated emergency communications outet—that residents shouldn't use landline phones or cell phones.

Traffic accidents were reported in the Mission Valley area, and major backups were reported on local freeways as offices emptied early.

Many radio stations were out, but KOGO said its offices and transmitter were running on a generator. 

All three Metropolitan Transit Service trolley lines were reported halted. Lindbergh Field stopped departures but not arrivals; some airlines canceled Friday morning flights, the Union-Tribune reported. People were advised to call their airlines.

San Diego State University shut down and won't have classes Friday. The University of San Diego also canceled Friday classes.

In La Mesa, the 99 Cent Store on Baltimore Drive and El Cajon Boulevard was open until dark amid long lines. 

Brandon Griffith, an employee at the store, said seven shoppers were allowed in, and as each shopper left another person was let in. He said 100 to 200 people came since the blackout started and people were buying ice, drinks, candles and flashlights.

La Mesa police Lt. David Bond said no major problems were reported, but all La Mesa police officers were being asked to check in for possible duty later.

"The La Mesa Police Department is only responding to life-and-death and emergency calls," Bond said. "So far so good. We have enough personnel [on duty], and we have people on standby."

One of the halted trolleys was stalled at Allison Avenue and Spring Street in downtown La Mesa.

Linda Gutierrez, who lives in downtown La Mesa, was one of those stranded at that trolley stop. She said: "When the trolley stopped, she said 'Oh no, another train will come up behind us and hit us."

She added that the train "stopped dead. ... It got real quiet and still."

She and other passengers said they were stranded and had no idea how they would get home.

SDG&E tweeted early in the incident: "We understand power is out, we are working on the cause and solution. We do not have a restoration time yet." It was several hours before SDG&E discussed the situation.

Phones were jammed throughout the county, and KOGO was told that Ensenada and other Baja California cities lost power.

A nurse at Sharp Memorial Hospital advised residents using oxygen tanks to move to police or fire stations with air conditioning because the tanks can explode in the heat, KOGO was told.

The California Highway Patrol reminded drivers to treat intersections with a flashing red light as stop signs. About 50 accident calls were pending "the last time I checked," a CHP spokesman told KOGO.

All schools in Alpine and the Grossmont Union High School District are closed Friday, but management is supposed to report to work, KOGO reported. Grossmont and Cuyamaca colleges and their child-care centers also are shut Friday, said district spokeswoman Anne Krueger.

Several beaches were closed for suspected sewage contamination, said Mark McPherson of the county Land and Water Quality Division late Thursday night.

"An estimated 3.2 million gallons of sewage spilled from the San Diego Metropolitan Wastewater System, Pump Station 64 on Roselle Street into the Los Penasquitos Lagoon," he said.

"The spill was discovered at 5:50 p.m. … and at this time is continuing," McPherson said in a news release (attached). "City of San Diego crews are working to control the release. As a result, all beaches north of Scripps Pier through Del Mar and Solana Beach will be posted at major beach access points."
 
Another sewage spill occurred at Pump Station 1 near Interstate 5 and state Route 54, leading to a release of an estimated 120,000 gallons.

"This spill flowed into the Sweetwater River, which flows into the San Diego Bay," McPherson said. "Signs warning of contamination will be posted at Bayside Park in Chula Vista and the San Diego Bay area accessed from Silver Strand."

Keep refreshing this story for latest updates.

Julie Pendray, Michelle Mowad, Hoa Quach, Deanne Goodman, Khari Johnson, Chris Jennewein, Kendal Patterson and other Patch editors contributed to this report, along with Adam Townsend.