As power returned, new headaches emerged. In New York's LaGuardia airport, backed-up planes meant long waits for passengers
The answer to the first question is still unknown, though the evidence so far points to a downed power line east of Cleveland that set off a chain reaction that darkened dozens of cities across the northeast, including New York, Toronto, and Detroit. A joint U.S.-Canadian task force has been formed to determine the cause of the outage.
The blackouts began around 4 pm, with early reports tracing the cause to a localized outage in a New York-area power plant, which destabilized the Niagara Mohawk Power Grid, which supplies electricity to much of the northeast United States. However, a spokesman for Governor Pataki said that the most likely cause for the incident was a problem with power transmission from a Canadian source. The Canadians insist that the problem started somewhere on the American side of the border, either from a lightning strike or a fire somewhere in New York or Pennsylvania. Power officials were unable to clear up the issue. "The disturbance appears to have been caused by the loss of several major transmission lines in the upper Midwestern United States, but investigations and data collections continue," the North American Electric Reliability Council, a private group which monitors the security of electric utilities, said in a written statement.
Regardless of its source, the blackout is one of the most extensive in U.S. history, shutting down at least 10 major airports and nine nuclear power plants in at least seven states and Canada's Ontario province.
In New York, power has returned to most of the city. Recovery in the rest of the region proceeds slowly. Cleveland faces its worst water crisis in years as electric pumps which siphoned water out of Lake Erie went offline, while Detroit officials dont expect to be able to restore power to parts of the city until Sunday. Across the border in Ottawa, the darkness brought criminals and vandals out onto the streets. "There is serious looting going on," said city police chief Vince Bevan Thursday, reporting break-ins, smashed windows and theft in the Canadian capital.
As power and services returned to the affected regions, officials and civilians were left wondering how the outages occurred — and whether they could happen again. "We're a superpower with a Third World [power] grid," New Mexico Governor and former energy secretary Bill Richardson told CNN. And with the shadow of September 11 hanging heavily over a darkened New York City, the blackout made many realize how vulnerable that grid could be. "I'm trying to keep calm," New Yorker Aaron David, 27, told the Associated Press. "But I was here for 9/11. This doesn't happen every day."