APS says a procedure being carried out by one of its employees at the North Gila substation near Yuma, AZ tripped a major 500kv power transmission line which serves San Diego Gas & Electric, causing a mass-scale power outage.
2-5 million people are affected by the outage, which persists at this hour all the way from southern Orange County (including San Clemente, San Juan Capistrano and Laguna Niguel) to the US-Mexico border, including the city of San Diego, and all the way from the California coast to Yuma, AZ.
Media outlets are reporting lines at gas stations, rushes on emergency supplies and traffic gridlock as people navigate tonight without street lights or traffic signals in one of the busiest metro areas in the country.
In addition to the SDG&E outage, the San Onofre nuclear reactors went into shutdown at 3:38pm, leading to further outages to the north, including some Southern California Edison customers.
People affected are being urged to activate their emergency plans, and are being advised that the outage could last into tomorrow.