LOS ANGELES (CBSLA) — Terminal 1 at LAX was evacuated early Thursday due to residual problems from a major power outage that lasted for nearly four hours Wednesday night.

Terminal 1, home to Southwest Airlines, was evacuated just before 6 a.m. due to problems with passengers and baggage not being properly rescreened. Airport officials decided Thursday to clear the terminal and rescreen all passengers by the TSA.

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Officials said LAX Airport police had to clear the terminal before all guests could be rescreened, a process they estimated would take an hour. In the meantime, all arriving passengers coming in to Terminal 1 were being held on their planes until rescreening resumes.

The terminals were cleared by 7 a.m. and passengers allowed back into Terminal 1 for rescreening.

Southwest Air says they had to cancel 11 flights and delay 15 others due to Thursday morning’s Terminal 1 rescreening.

The power outage hit the airport at about 6:30 p.m., hitting the Southwest and United terminals the hardest. Eighteen Southwest flights were canceled. Among United flights, three were canceled, seven were diverted and 15 more were delayed, officials said.

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The outage affected everything from jetways, forcing passengers to use stairs to deplane, to traffic signals, leading to backups throughout the airport.

Passengers say they arrived for their flights early, as is generally advised, only to find the windows of terminals black. Traveler Kathy Osorio says she had no idea what was happening.

“We were just following the crowd. We followed two to the other terminals and they told us they didn’t know what they could do for us. So we had to come back here,” she said.

The cause of the power outage was blamed on a power surge at an off-airport Los Angeles Department of Water and Power substation, which caused a power disruption throughout the airport. A total of 21 flights were canceled and at least seven others were diverted, an airport official said.

Power was restored to most of the airport by about 10 p.m.

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Officials at LAX say one lane may be closed on Century Boulevard between Sepulveda Boulevard and Vicksburg Avenue at some point Thursday for repair work by the LADWP on the primary power line that serves the airport.