SAN DIEGO – Utility crews brought electricity back to much of California, Arizona and Mexico on Friday, a day after a power outage left millions in the dark, paralyzed freeways and halted flights at San Diego's airport.
Officials, however, warned that the electrical grid was still too fragile and asked residents and businesses to go easy on -- or even put off using -- major appliances, such as air conditioners.
"Conservation will really help reduce the strain," said Stephanie McCorkle at the California Independent System Operator, which manages the power grid.
Electricity came back in San Diego early Friday, signaling that the blackout was essentially over because most people affected were in the nation's eighth-largest city. City schools, state universities and community colleges in the area remained shuttered. Beaches were closed because the outage caused a 3.2-million gallon sewage spill.
Mexico's electrical utility said the lights are on for 1.1 million customers, or 97 percent of those who lost power. Power was also restored to all 56,000 customers in Yuma, Ariz.
The San Diego area was hit especially hard with power severed about 4 p.m. Thursday to all of San Diego Gas & Electric Co.'s 1.4 million household and business customers.
That left residents sweltering without air conditioners and paralyzing some freeway and airport traffic.
The outage extended into southern Orange County, across California's inland deserts, as far east as Yuma and into Mexico. The region is home to 6 million people, though it was impossible to say exactly how many had lost power.
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, sparked such a widespread outage. The company said that would be the focus of an investigation.
"This was not a deliberate act. The employee was just switching out a piece of equipment that was problematic," said Daniel Froetscher, an APS vice president.
It's possible that extreme heat also may have caused some problems with the transmission lines, said Mike Niggli, chief operating officer of San Diego Gas & Electric Co.
During the night, much of San Diego was in darkness, and all outgoing flights grounded at its main airport, Lindbergh Field. The airfield was open and had power Friday morning but authorities said some airlines may have cancelled flights.
There were no immediate reports of major injuries connected with the outage. Officials in San Diego and elsewhere said they were on alert but no major problems had arisen, including any signs of looting or other unrest.
There were reports of minor traffic accidents as the outage caused mayhem on the streets without stoplights during rush hour.
Leah Walden, 59, said she saw about five fender-benders on her drive from her accounting job in suburban Spring Valley to a wedding-cake tasting in San Diego.
"People are irritated. They don't want to wait," said Walden, adding that about 15 cars went into reverse on a freeway veering out of the way of oncoming traffic to escape traffic jams. "That's how nuts people are."
In the beach town of Encinitas north of San Diego, Tim Grenda, 41, put a positive spin on it, pointing out that his hot yoga class was cooler because of the outage. The class, usually performed at 104 degrees, was closer to 99 degrees because a furnace used to pump in heat had been knocked out.
"It was hot enough for me, but it wasn't quite as intense as the usual practice," he said.
Rosa Maria Gonzales, a spokeswoman with the Imperial Irrigation District in California's sizzling eastern desert, was less enthusiastic -- temperatures were well into triple-digit territory when the power went out.
"It feels like you're in an oven and you can't escape," she said.
The blackout extended south of the border to Tijuana, Mexicali and other cities in Mexico's Baja California state, which are connected to the U.S. power grid, Niggli said. Police on both sides sent in re-enforcements to prevent looting and other crime in their cities, but none was reported.
In the border city of Tijuana, people formed long lines outside convenience stores Thursday, trying to buy ice or take advantage of beer being sold at half price. Many people drank that beer on the streets or in parked cars with speakers booming loud music.
Cars also formed snaking lines at the few gas stations with generators that remained open and traffic snarled streets after traffic lights stopped working.
Jose Padilla Flores, who was one of the few people who still had electricity Thursday, was offering to let people watch the telenovela on his television if they bought fried tacos and flavored water from his small restaurant "El Dorado" in the Independencia neighborhood.
"My female neighbors were the first ones to ask if I could let them watch the telenovela," said Padilla Flores, 35. "I thought that was a great idea to promote my business."
San Diego residents poured into the few bars that remained open downtown after dark, some donning 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.
"It's surreal," said Myrna Contreras, 35, sitting in the patio of a candlelit bar. "It's upbeat. It's friendly."
Two reactors at a nuclear power plant along the coast went offline after losing electricity, but officials said there was no danger to the public or workers.
The outage came more than eight years after a more severe black out in 2003 darkened a large swath of the Northeast and Midwest. More than 50 million people were affected in that outage.
In 2001, California's failed experiment with energy deregulation was widely blamed for six days of rolling blackouts that cut power to more than 3 million customers and shut down refrigerators, ATMs and traffic signals.