After almost 29 hours without power, all of New York City's electricity is restored.

Subways began operating after midnight, and by dawn Saturday were running with only minor interruptions. Delays continue at New York area airports, however.

Power also has been restored to the rest of New York State and most areas of seven other states and parts of Canada that were hit by North America's worst-ever power outage, which affected 50 million people.

While officials continue to investigate the cause of the massive blackout, New York City Mayor Michael Bloomberg cautioned against assigning blame to New York's local electric company.

"It's one of those things, everybody likes to criticize them," he said. "I think they actually did a good job. I'm sure they could have done some things better. They had to deal with their outside suppliers."

The search for answers continues. The power outage occurred along a giant electrical grid that links New York, Michigan and the Canadian province of Ontario. Friday, the United States and Canada formed a joint task force to investigate vulnerabilities in the system.

U.S. Energy Secretary Spencer Abraham, in New York State Saturday, says finding out the causes and the effects could take awhile.

" I don't think we have an estimation yet," he said. "These things typically will take some time. We, obviously, are happy that most of the systems are back and operational. One of the other challenges our department is working on is identifying the secondary impacts, for instance in the Midwest, the impact on gasoline refineries, the availability of gasoline. It's too early to project out what those kinds of costs might be, but we know that they will be borne."

Governor Pataki says the area's state of emergency will continue, while power demands remain high in hot and humid weather. He also applauded New Yorkers for making conservation efforts, even after the power came on.

" It was a joint response, it was New Yorkers all standing together as a team, caring their neighbors, caring about their families, caring about each other, and being willing to conserve energy that allowed us to get through this in such exemplary fashion," he said.

New Yorkers seeking relief from the heat are crowding city swimming pools, but swimming at city beaches remains off-limits for the second straight day because of the danger posed by high pollution levels. While the power was out, two sewage treatment facilities malfunctioned, depositing millions of gallons of raw sewage into the water.

Garbage trucks began collecting trash early Saturday, trying to clean up the excess of spoiled food that New Yorkers had to throw out.