Electrical power is slowly being restored to New York City and other parts of the eastern and midwestern United States affected by Thursday's massive power outage. The power failure cut electricity to 50 million people in the United States and Canada.

Power problems persisted from Connecticut and New York in the east, to Michigan and Ohio in the midwest, and north up into Canada. Energy officials say it will take a while yet to restore full power.

In New York City, police and firefighters were inundated with twice the usual number of emergency calls overnight, and there were more than 800 elevator rescues.

But Mayor Michael Bloomberg said, for the most part, the city was coping with the outages, and he urged non-essential city workers to stay home Friday.

"In short, New Yorkers showed that the city that burned in the 1970's when facing similar circumstances is now a very different place, a city that has resiliency to conquer adversity and not succumb to it, like we did back then," he said.

In Cleveland, Ohio, the concern was water. Although power is now being restored in the city, it may be a while before pumping stations can resume the water flow to residents.