Michael Bloomberg

New York City Mayor Michael Bloomberg says power could be back on in his city in just hours.

He says a power failure along the New York-Canadian border cascaded through the power grid across the northeast United States and parts of Canada. He says investigators do not yet know what caused the first outage.

Mr. Bloomberg stressed there is no evidence of terrorism "whatsoever." He also dismissed earlier reports of a fire at a major New York City power plant.

The mayor says there have been no reports of increased crime. But he added that the New York Police Department has fully mobilized and positioned officers across the city.

Mayor Bloomberg spoke to reporters almost two hours after the city lost power and tens of thousands of people poured into streets and the blistering summer heat. He says rescuers are working to free people trapped in subways and elevators.

U.S. federal aviation authorities also suspended flights into six major airports in the affected region, including the New York area's John F. Kennedy, Laguardia and Newark airports.

Several other cities also lost power, including Cleveland, Detroit, Erie (Pennsylvania), Toronto and Ottawa.