Power is slowly being restored Friday, across the northeastern United States and Canada, where a huge power grid failure cut electricity service to 50 million people from New York to Toronto to Detroit.
Reports indicate the blackout was the largest ever to hit North America. U.S. officials say there was no evidence of any terrorist activity, but more than 15 hours after the lights went out late Thursday, there was no specific explanation for the power failure.
Power company officials also discounted the possibility that a computer "worm" - a virus-like attack on computer systems spread over the Internet - could have caused the blackout.
Despite the widespread outage, reports of crime throughout the area have been low, and there are no reports of any major disturbances.
Six major airports were closed by the power problem, and that triggered a cascade of delayed or cancelled flights across the country and even across the Atlantic Ocean. Subways, elevators and traffic signals stopped in New York, and other cities reported problems with water supplies. The circuit-breaker action that turned off the power grid that distributed electricity supplies around the country also resulted in an automatic shutdown at nine nuclear plants.
The governor of New York state, where 19 million people were affected by the blackout, said he was not aware of any fatalities caused by the outage, which coincided with one of the hottest days of the year.
Governor George Pataki said New Yorkers' "courage and calm" helped the region survive the power crisis. His comments were echoed by authorities in other states.
Power returned to New York's Times Square shortly before 12:00, Universal Time 15-and-one-half hours after the blackout began. However, officials say it may take several days to restore power fully in the cities of Detroit, Michigan, Cleveland, Ohio, and other areas.