A major portion of Los Angeles (search) lost power Monday afternoon after utility workers connected the wrong wires.

Outages were reported at about 12:30 p.m. from downtown to the coast and north into the San Fernando Valley (search), an area encompassing about 2 million residents and thousands of businesses, according to the Los Angeles Department of Water and Power.

Much of the power was restored within about 21/2 hours; all power was expected to restored by 5 p.m.

Several workers who were installing an automated transmission system hooked up the wrong wires, according to Ron Deaton, general manager of the Department of Water and Power.

"They connected it to another line that was not expecting that much electricity," he said. No injuries were reported.

Calm prevailed in downtown Los Angeles around midday. Office workers took the opportunity for an extended lunch as police and fire sirens echoed in the background.

Los Angeles International Airport lost power, but its emergency generator kicked in promptly and no flights were affected, said Harold Johnson, an airport spokesman. UCLA Medical Center used backup generators and reported no danger to patients.

Terrorism was not suspected, according to police Sgt. Catherine Plows, though the Los Angeles Police Department went on "full tactical alert," meaning no officers were allowed to leave duty.

Fire officials said they received reports of people stuck in elevators and traffic was snarled at intersections throughout the city when stop lights went dark. Neighboring cities, including Burbank and Glendale, also were affected.

The weather did not appear to be a factor; skies were overcast in the region.

Stephanie McCorkle, spokeswoman for the California Independent System Operator, said grid managers were watching the outage closely, but had no additional information.

When power went out, some feared there was a connection to terrorism — a concern made stronger because of a newly discovered video tape purportedly made by an American member of Al Qaeda.

ABC News on Sunday broadcast a tape that featured a masked man making terrorist threats against Los Angeles and Australia. The man is believed to be Adam Yahiye Gadahn (search), an American from California purported to be an Al Qaeda member and wanted by the FBI. The CIA said Sunday it was aware of the report but had no immediate comment about the tape's authenticity.

The man on the tape, wearing a black turban with most of his face covered, calls the Sept. 11 attacks of four years ago "blessed events" before making a threat against the U.S.

"Yesterday, London and Madrid. Tomorrow, Los Angeles and Melbourne, Allah willing. And this time, don't count on us demonstrating restraint and compassion," the man said during the 11-minute tape.

But even before the utility explained what happened, Homeland Security Department spokesman Russ Knocke said said there was no indication of terrorism.

Some Los Angeles neighborhoods did not lose power at all.

Los Angeles operates its own power utility, which serves 1.4 million electricity customers. Customers of Southern California Edison, the largest utility in Southern California, were not affected, according to spokesman Gil Alexander.

Katie Cerio, a stylist for TV commercials, said traffic lights were out in the Torrance neighborhood.

"They've got people directing traffic, but it's definitely a bit chaotic," Cerio said as she drove. "But now I just entered West Hollywood and the traffic lights seems to be on."

At the downtown YMCA, staff used flashlights to help usher exercisers from the pool and other areas to locker rooms so they could dress before leaving.

Inside some high-rises, office workers were stuck in elevators. Albert Vasquez, 27, a customer service representative, was returning from lunch when he boarded an elevator — and the doors closed and the power went out.

"It was bizarre," he said. "It went completely dark."

Vasquez said he pried open the doors with his hands and left the building.

Across the city, traffic was snarled at intersections when stop lights went dark.

Katie Cerio, a stylist for TV commercials, said traffic lights were out in the valley's Torrance neighborhood.

"They've got people directing traffic, but it's definitely a bit chaotic," said Cerio as she drove. "But now I just entered West Hollywood and the traffic lights seems to be on."

Gas station pumps stopped working, car washes stopped in their tracks, assembly lines ground to a halt and restaurant machinery quit in middle of lunch hour.

At Bob's Big Boy restaurant in Burbank, power was out for about 90 minutes.

"All we could serve were salads and cold sandwiches," manager Frank Rodriguez said. "No hamburgers."

The Associated Press contributed to this report.