San Diego Gas and Electric President Mike Niggli explains the cause of the outage and how long it will take to come back online.
Federal regulators plan to investigate the massive power outage that left millions of people in the dark.
The Federal Energy Regulatory Commission (FERC) announced on Friday they would work with the North American Electric Reliability Corporation, to try to figure out what happened.
If any regulatory violations are found, the commission could issue fines of up to $1 million per day for every violation, according to FERC spokeswoman Mary O'Driscoll.
In addition, the California Independent System Operator Corporation initiated a joint task force to investigate the widespread blackout.
ISO will bring together all of the utilities impacted by the outage, including San Diego Gas & Electric. Findings from the investigation will be made public when available.
The massive blackout lasted 15 hours and plunged 1.4 million San Diego residents into darkness.
San Diego Gas & Electric announced Friday morning that all of its customers have power again after crews worked through the night to make emergency repairs following the accidental outage.
The San Diego Police Department said there were no major incidents over night, despite the blackout.
"There was nothing that was blackout-related that was anything more than normal," said SDPD Lt. Andra Brown. "We did not see an increase in violence or activity due to blackout."
All stations are operating like normal.
"We were fully operational receiving 911 calls and dispatching services throughout the blackout," Brown said. All of the stations have emergency generators, so can still receive/process/book prisoners. As long as the patrol cars have gas, they've got ability to get around."
The blackout also caused a sewage spill that 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.
The outage occurred after an electrical worker removed a piece of monitoring equipment at a power substation in southwest Arizona, officials at Phoenix-based Arizona Public Service Co. said. It was unclear why that mishap, which normally would have been isolated locally, sparked such a widespread outage. The company said that would be the focus of a probe.
The outage knocked out power in a region of almost 6 million people in the Southwest, bringing San Diego to a near-standstill and leaving people in the surrounding desert to swelter in late-summer heat.
Power slowly returned as the outage wore on. By 8 p.m., officials were reporting that power had been restored to parts of Oceanside, Eastlake and the Chula Vista community of Bonita. At about 10:30, SDG&E tweeted that residents in Encinitas, Carlsbad, San Marcos, Escondido, Rancho San Diego had their power back, while in South Bay, electricity had been restored in National City. By 2:30 in the morning, half of SDG&E's impacted customers had power again.
San Diego Mayor Jerry Sander held a media conference at 8 p.m., saying that as a precautionary measure prompted by problem with water pumps, city residents living in the communities of Otay Mesa, Scripps Ranch, La Jolla, Mount Soledad, Tierresanta and Scripps Ranch were under a mandatory boil-water order.
Water issues were also paramount at several communities that were located far from pumping stations. Residents of Fallbrook, Ramona, Valley Center, and Coronado were being urged to conserve water in whatever ways possible.
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 widespread outages in the region.
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, Southern California Edison said.
The shutdown was proceeding "safely" and "poses no danger to workers or the public," Edison said in a statement. "Offsite power is available for the plant's safety systems."
The FBI and SDG&E officials said the power outage was not related to a terror threat that officials notified the nation about at nearly the same time.
Earlier in the day, Sander's office asked people to stay off roads and to not use land-line phones.
San Diego City Hall was voluntarily evacuated after the outage. Some people were trapped in elevators inside the building but were later freed by firefighters.
William Burke, with MTS security, said transit officials were trying to get buses moving as quickly as possible to take passengers to their destinations. They're trying to mobilize the buses as quickly as possible to get passengers "home before dark." Trolleys, of course, are powered by electricity and all service was out.
The San Diego border along Mexico remained open, operating under backup power, authorities with the U.S. Customs and Border Patrol said.
San Diego's international airport remained open during the blackout, but no outbound flights were taking off. Some inbound flights were delayed or diverted, officials said.
San Diego State University closed for the day, and local schoolchildren around the county were dismissed as well. No injuries from the school were reported.
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."
Roads and freeways became congested throughout the county after traffic lights went out, but the commute was a nightmare for thousands.
Things were not so serious in some spots, though. In the Gaslamp, for example, many bars remained open for "blackout parties," with people passing the night in the company of their fellow "sufferers." There was little traffic in the streets, with laughter heard on many street corners where passers-by were overheard sharing their stories. Still others donned reading lights on their heads like miners. A pair of men carried flaming Tiki torches -- usually planted in backyards -- to see their way down the pitch-black street.
Send us your photos and check back for updates on this breaking story.