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Passenger Michael Moretti waits at the baggage pick-up at San Diego International Airport after a massive blackout hit Southern California Sept.8, 2011.
San Diego -- Officials have a complete breakdown of streets in areas of the county affected by boil-water advisories. Click here for a complete list of areas and street listings.

Power was fully restored in San Diego County Friday following a historically severe blackout that left some 5 million people without electricity from Mexico to southern Orange County and prompted a federal probe into its cause.

Despite the restoration, public elementary, middle and high schools remained shuttered in the region Friday, along with federal courts, authorities said. That decision was made Thursday, when San Diego Gas & Electric reported that the outage could continue through Friday and even into Saturday.

County courts and other government agencies, however, were open for business as usual.

Stating that the Southland's energy system remained "fragile" in the aftermath of the massive outage, SDG&E officials asked their customers to restrict electricity usage as much as possible Friday as a precaution. The utility operates 1.4 million electric meters and more than 850,000 natural gas meters in San Diego and Orange counties.

The unprecedented outage struck around 3:40 p.m. Thursday. At 3:30 a.m. Friday, San Diego Gas & Electric reported that all power in San Diego County had been restored.

The outage knocked out power to homes and businesses in San Diego, Orange and Imperial counties, parts of Arizona and Baja California.

It also shut down the two reactors at the San Onofre nuclear power plant, though the facility did not lose power or experience safety issues, according to its operator.

On Friday morning, the Federal Energy Regulatory Commission announced that it would conduct a "full" investigation into the outage along with the nonprofit North American Electric Reliability Corp.

In seeking to determine what caused the system breakdown, the agencies will coordinate with the Department of Energy and other federal agencies, the California ISO, the Western Electricity Coordinating Council, California and Arizona state regulators and companies involved to monitor the situation, officials said.

"This inquiry is an effective way for us to protect consumers and ensure the reliability of the bulk power system," FERC Chairman Jon Wellinghoff stated.

During the outage, schools and businesses -- including gas stations -- closed; commuters jammed roadways; medically fragile people packed hospitals; and at least two sewage pumps failed, contaminating a lagoon and a river that feeds into San Diego Bay.

There were several reports of people stuck in elevators and on San Diego Trolley cars, and Lindbergh Field virtually shut down for a time.

Following safety checks completed overnight, North County Transit District officials announced that normal Coaster and Sprinter service would resume Friday morning. But there could additional isolated outages through the day, SDG&E reported.

Following restoration of electrical service throughout the region, residents were encouraged to avoid the use of air conditioners if possible, or set them no lower 78 degrees if structural cooling was absolutely necessary. Major appliances, such as washer and dryers, should not be used Friday, according to SDG&E.

The utility set up a phone number for customers to call if they experience further outages. The number is 1 (800) 411-SDGE.

The California Independent System Operator, which manages the state's power grid, blamed the outage on the failure of a high-voltage power line between Arizona and Southern California, saying it affected all SDG&E customers and the customers of other utilities as well.

"The outage was triggered after a 500-kilovolt (kV) high-voltage line from Arizona to California tripped out of service. The transmission outage cut the flow of imported power into the most southern portion of California, resulting in widespread outages in the region," according to Cal ISO.

The Arizona power company APS said the outage appears to have been related to a procedure an employee was carrying out in the North Gila substation northeast of Yuma.

Operating and protection protocols typically would have isolated the resulting outage to the Yuma area. The reason that did not occur in this case will be the focal point of an investigation now under way.

However, not everybody believes one man could start such an outage.

"It wasn't one guy in Arizona who tripped the system and caused San Diego to collapse," Michael Shames with the Utility Consumers' Action Network said.

The Arizona Power Service said the worker was replacing a broken capacitor -- a device that regulates the voltage on the transmission system -- but they still do not know what caused it to short circuit.

An Arizona Power Service spokesman said calling the outage human error would be premature, that they still need several days, if not weeks, to investigate.

San Diego police Officer David Stafford said downtown's Gaslamp Quarter was particularly busy Thursday night into early this morning as many residents and tourists flocked to bars to pass the time.

There were several burglaries reported around the city throughout the night, but Stafford said early today it was too soon to tell if the outage was the reason.

The sheriff's department received reports of a glass door broken at a taco shop in Lemon Grove and a report of a home break-in Vista following the outage.

The SDPD reported a burglary in the Kensington area. Neighbors reported hearing someone inside the home of a neighbor that was out of town. One man was arrested after having property from the home in his possession.

Another burglary was reported at San Diego Trailer Supply on El Cajon Boulevard. Two men and a woman was reported seen leaving the store with merchandise around 11:45 p.m. The three suspects got away.

SDPD reported possible looting at the Infinity Wellness Center located in the 9400 Block of Black Mountain Road just after midnight.

Authorities issued a statement advising the public that the county had declared a local emergency, meaning that any looting would be treated as a felony.

The National University System Institute for Policy Research estimated the economic impact of the power outage to be between $97 million and $118 million.

Most of those costs come from perishable food loses, government overtime and a general loss of productivity.