(Photo of flooding in New York City's financial district is courtesy of NBC News. For more photos from NBC, click here.)

President Barack Obama declared a major disaster in the New York City area Tuesday as Superstorm Sandy pounded the Northeast, killing at least 28 people, sweeping homes into the ocean, flooding large swaths of coastal areas, crippling public transit, and leaving millions without power.

As the East Coast woke up, residents faced the prospect of up to a week without heat, light or refrigeration, while authorities tried to measure the full wrath of the once-in-a-generation hurricane.

The deaths included at least 10 people in New York City, Mayor Michael Bloomberg said Tuesday, adding "tragically, we expect that number to go up."

Details of the devastation were also becoming clear:

• More than 8.1 million homes and businesses were without power across 17 states, and nearly half of the outages were in New York and New Jersey, according to a tally by the federal government. NBC News meteorologist Bill Karins warned to "expect the cleanup and power outage restoration to continue right up through Election Day."
• A massive fire destroyed at least 50 homes in Breezy Point, a seaside community in Queens, N.Y. Firefighters had difficulty reaching the blaze due to the severe weather. The cause of the fire was not immediately known.
• Seven subway tunnels under the East River in New York City were flooded, leading MTA Chairman Joseph Lhota to declare: "The New York City subway system is 108 years old, but it has never faced a disaster as devastating as what we experienced last night." Subway service was unlikely to resume for 4 to 5 days, Bloomberg said.
• PATH train service between Manhattan and New Jersey is likely to be suspended for 7-10 days, Gov. Chris Christie said Tuesday.
• Half of Hoboken, N.J., was underwater, preventing emergency crews from reaching areas of the city, according to Mayor Dawn Zimmer. "We want people to be aware that it's a very dangerous situation," she told MSNBC.
• At least four towns in north New Jersey — Moonachie, Little Ferry, South Hackensack and Hackensack — were submerged by up to 6 feet of water after a levee broke.
• New York University Medical Center evacuated 215 patients to other hospitals because its backup generator was out. Critical patients — including infants in neonatal intensive care — were taken to Mount Sinai Hospital, Memorial Sloan-Kettering and New York Presbyterian Hospital.
• The storm surge destroyed several homes on Fire Island, N.Y., where some people had decided to sit out Sandy.
• More than 15,000 flights have been canceled so far and New York City's airports remained closed Tuesday. Rail traffic was also heavily affected, with Amtrak canceling all of its Northeast Corridor service, in addition to some other lines.
• Rising waters sparked an alert at the Oyster Creek nuclear power plant in New Jersey Monday night, the Nuclear Regulatory Commission said. The alert was the "second lowest of four NRC action levels," it added, and was "due to water exceeding certain high water level criteria in the plant’s water intake structure." Exelon said there was no danger to equipment and no threat to public health or safety.

The dollar value of Sandy's destruction was still unclear.

"I think the losses will be almost incalculable," New Jersey Gov. Chris Christie told NBC's TODAY show.

One disaster forecasting company predicted economic losses could ultimately reach $20 billion, Reuters said .

The historic storm, which made landfall at 6:45 p.m. ET Monday, hurled a wall of water of up to 13 feet high at the Northeast coast.

Tuesday's disaster declaration for New York City means that federal funds will be available to people affected by the storm, according to a White House statement.

"This was a devastating storm, maybe the worst that we have ever experienced," Bloomberg said, adding that schools would be closed Tuesday and Wednesday.

Seawater surged into lower Manhattan and areas of Brooklyn, submerging entire streets and parks Monday. An all-time record tide level of 13.88 feet was set at The Battery in Lower Manhattan, Monday night, breaking the previous record of 11.2 feet from 1821, as well as Sandy Hook, N.J., shattering the previous record from the Dec. 1992 Nor'easter and Hurricane Donna in 1960, according to weather.com.

New York City's major utility said damage to its power infrastructure was "unprecedented."

On Long Island, 90 percent of homes were without power, Gov. Andrew Cuomo said Tuesday.

In New Jersey, two thirds of all utility customers, nearly 2.5 million homes and businesses, were without power.

Around midday, Sandy was about 120 miles east of Pittsburgh, pushing westward with winds of 45 mph, and was expected to make a turn into New York state on Tuesday night. Although weakening, continued heavy rain and flooding is expected over the next day.

In a measure of Sandy's immense size and power, waves on southern Lake Michigan rose to a record-tying 20.3 feet.

High winds clobbered the Cleveland area early Tuesday, uprooting trees, cutting power to hundreds of thousands, closing schools and flooding major roads along Lake Erie.

Blizzard warnings were also posted for the mountains of West Virginia, western Virginia and Garrett County, Md. More than 2 feet of snow was reported in parts of West Virginia.

The powerful storm flooded sections of Atlantic City and other areas of the New Jersey shore. Part of the Atlantic City boardwalk was washed away.

Christie sharply criticized Atlantic City Mayor Lorenzo Langford, whom he blamed for having "advised people to stay in shelters in the city."

"Despite my admonition to evacuate, he gave them comfort, for some reason, to stay," Christie said, NBCPhiladelphia.com reported.

NBC News has been able to confirm 28 deaths so far along the East Coast:

• New York City (10): A woman, 75, in Manhattan died when power to her oxygen machine failed, while a man, 55, was found dead in a flooded basement in Lower Manhattan and a girl, 14, was found dead near the shoreline in Staten Island, according to NBCNewYork.com. Two men, one in Queens and one on Long Island, were killed by falling trees, and a woman was electrocuted in Queens when she stepped into water that concealed a live wire. Details on the other deaths were not immediately available.
• New York state (5): Five people died in other parts of the state, Gov. Cuomo said Tuesday. Two boys were killed in North Salem, N.Y., when a tree crashed into the home they were in, NBCNewYork.com reported. Details on the other deaths were not available.
• New Jersey (3): Two people died when a tree fell on their car in northern New Jersey, authorities told NBCPhiladelphia.com. Christie told NBC that a third person died as well, but details were not available.
• Pennsylvania (2): A man, 62, and a boy, 8, were killed by falling trees, NBCPhiladelphia.com reported.
• Connecticut (2): A woman, 90, and a firefighter were killed by falling trees, NBCConnecticut.com reported.
• Virginia (2): Officials said two traffic deaths were tied to Sandy but no details were available.
• Maryland (2): A man was killed by a falling tree and a woman died in a traffic accident, NBCWashington.com reported.
• West Virginia (1): A woman died in an accident on snow-covered roads in Tucker County, NBC station WSAZ reported.
• At sea (1): One person died when a replica of the HMS Bounty sank 90 miles southeast of Hatteras, N.C. Fourteen others were rescued, but the captain was missing.

Before it made its way north, Sandy was blamed for the deaths of 65 people in the Caribbean.