The sun shone again over New York today, as the city and much of the US East Coast took the first steps back to normality after being battered by superstorm Sandy.

It was a striking sight after days of grey skies, driving rain and fierce winds that killed 61 people across the region.

Two major airports reopened and the New York Stock Exchange came back to life, but the National Guard was still searching wrecked buildings in New Jersey for more survivors, or victims.

At the stock exchange, running on generator power, mayor Michael Bloomberg gave a thumbs-up and rang the opening bell to cheers from traders on the floor. Trading resumed after the first two-day weather shutdown since the Blizzard of 1888.

Kennedy and Newark airports reopened with limited service morning. New York's LaGuardia Airport, which suffered far worse damage and where water covered parts of runways, remained closed.

It was clear that restoring the region to its ordinarily frenetic pace could take days - and that rebuilding the hardest-hit communities and the transportation networks that link them together could take considerably longer.

About 6.5 million homes and businesses were still without power, including 4 million in New York and New Jersey. Electricity was out as far west as Wisconsin and as far south as the Carolinas.

The scale of the challenge could be seen in New Jersey, where National Guard troops arrived in the heavily flooded city of Hoboken to help evacuate thousands still stuck in their homes and deliver ready-to-eat meals. Live wires dangled in floodwaters that Mayor Dawn Zimmer said were rapidly mixing with sewage.

Thousands of people were still holed up in their homes in the city across the Hudson River from New York.

And new problems arose when firefighters were unable to reach blazes rekindled by natural gas leaks in the heavily hit shore town of Mantoloking. More than a dozen homes were destroyed.

President Barack Obama was due to visit New Jersey, which was directly in the storm's path on Monday night and where part of the historic boardwalk washed away.

As New York began its second day after the storm, morning rush-hour traffic was heavy as people started returning to work. There was even a sign of normality: commuters waiting at bus stops.

On the Brooklyn Bridge, closed earlier because of high winds, joggers and bikers made their way across the span before sunrise. Car traffic on the bridge was busy, and slowed as it neared Manhattan.

A huge queue formed at the Empire State Building as the observation deck opened for the first time since the storm.

The Brooklyn-Battery Tunnel, connecting Brooklyn to Manhattan, and the Holland Tunnel, between New York and New Jersey, remained closed. But bridges into the city were open, and city buses were running, free of charge.

School was cancelled for a third straight day in the city, where many students rely on buses and subways to reach classrooms.

Mayor Bloomberg said it could take four or five days before the subway, which suffered the worst damage in its 108-year history, is running again. High water prevented inspectors from immediately assessing damage to key equipment.

Power companies said it could also be the weekend before electricity is restored to Manhattan and Brooklyn, perhaps longer for other New York boroughs and the New York suburbs.

In Connecticut, some residents of Fairfield returned home in kayaks and canoes to inspect widespread damage left by retreating floodwaters that kept other homeowners at bay.

"The uncertainty is the worst," said Jessica Levitt, who was told it could be a week before she can enter her house. "Even if we had damage, you just want to be able to do something. We can't even get started."

And in New York, residents of the flooded beachfront neighbourhood of Breezy Point returned to find fire had taken everything the water had not. A huge blaze destroyed perhaps 100 homes in the close-knit community where many had stayed behind despite being told to evacuate.

John Frawley, who lived about five houses from the fire's edge, said he spent the night terrified "not knowing if the fire was going to jump the boulevard and come up to my house."

"I stayed up all night," he said. "The screams. The fire. It was horrifying."

There were still only hints of the economic impact of the storm.

Forecasting firm IHS Global Insight predicted it would cause 20 billion dollars in damage and up to 30 billion dollars in lost business.