A power cut hit much of Los Angeles yesterday, blocking people in elevators for up to two hours and causing tailbacks as traffic lights went down.
Authorities blamed a power cable that was 'accidentally' cut but the blackout came as a new shock to the nation two years after power cuts in the northeast that lasted several days.
The blackout hit a large part of metropolitan Los Angeles and the San Fernando Valley. The lights went out at 12.37pm (local time) and remained out for about two hours in most areas.
City maintenance workers had accidentally cut a line at a receiving station, then connected it to another line 'that was not expecting that amount of electricity'.
The surge triggered outages that knocked out service to more than 2m people in parts of Los Angeles and its immediate suburbs.
An Al-Qaeda videotape released last Sunday had promised an attack on Los Angeles, but authorities quickly reassured the public that terrorism was not suspected.
Police put their forces on a tactical alert, with all officers ordered to remain on duty until further orders and only emergency calls answered.
Many offices and schools came to a standstill and traffic lights also went out at traffic junctions on busy streets causing jams in a city where tailbacks are notorious.
Lights flickered at Los Angeles International Airport before backup power came on. The rail system was also able to keep running with emergency power.
The US has suffered a number of power crises in recent years and energy shortages are becoming an increasing concern in Congress.
In August 2003, 50m homes lost power in New York and other parts of the northeast US. Tens of thousands of people slept on the streets of New York the first night because they could not get home.
The breakdown was traced back to a problem at a power station in Ohio that rippled through the entire grid in the region.
California imposed rolling power cuts in 2001 because of a chaotic deregulation scheme that forced power producers in the state to sell much of their output, the effect of a drought and several other circumstances that put critical strains on the power grid.