WATCH: Flooding caused a massive explosion at New York's Con Edison power station.
President Barack Obama has declared "a major disaster" in New Jersey and New York State after a massive storm smashed into the east coast of the United States.
The measure makes federal funds available to residents of the hardest hit areas.
Sandy is the largest Atlantic storm ever to hit the northeastern United States.
At least 28 people have been reported killed across several U.S. states and Canada since the storm hit New Jersey on October 29.
Heavy winds left more than 6 million people without electricity.
In New York City, seawater flooded much of the subway system and road tunnels.
Mayor Michael Bloomberg said on October 30 that the subway would be unlikely to resume service for four-to-five days.
A power substation exploded and firefighters said a blaze destroyed some 50 homes.
Trading at the New York Stock Exchange was suspended again on October 30. It is the first time the exchange suspended operations for two consecutive days due to bad weather since the late 1880s.
WATCH: Storm wreaks havoc across Northeast
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Hurricane Sandy Causes Flooding, Damage
Over the past 48 hours, thousands of flights have been canceled or disrupted.
New York City's three major airports remained closed on October 29.
Operators shut down units at several nuclear power plants as a safety precaution.
In the wake of the storm, up to a million people had been ordered to evacuate their homes.
But by the time Sandy was reaching its peak late on October 29, New York Mayor Michael Bloomberg said evacuations were no longer possible.
"If you're in your home or somewhere safe where you can remain, stay there," he said. "The time for relocation or evacuation is over. Conditions outside are dangerous and they are only going to get worse in the hours ahead."
The full extent of the damage is still not clear. Analysts say it is expected to be amount to tens of billions of dollars.
Sandy has disrupted campaigning just one week before the U.S. presidential elections.
Both Obama and his Republican Party challenger, Mitt Romney, have canceled campaign events as a result of the storm.
