RICHMOND, Va. - Hurricane Isabel knocked out power to more than 3.5 million people as it weakened into a tropical storm and raced up the Eastern Seaboard on Friday, swamping tidal communities along Chesapeake Bay, uprooting trees, disrupting air traffic and shutting down the nation's capital.

The massive storm was blamed for at least 14 deaths: nine in Virginia; two in Maryland and one each in New Jersey, North Carolina and Pennsylvania.

The storm plowed into North Carolina's Outer Banks on Thursday night with winds of about 100 mph and moved across Virginia early Friday as its winds eased to around 40 mph. It began moving into western Pennsylvania and was expected to sweep through western New York state before dissipating in Canada by Saturday.

Michael Brown, director of the Federal Emergency Management Agency, said Isabel inflicted the worst damage along the Outer Banks.

"Our concern down there is we have about 4,000 people who refused to evacuate. We're getting in to make sure they're OK," he said on ABC's Good Morning America.

Brown cautioned that residents in Isabel's path should keep their guard up, with flood waters moving into tributaries throughout the day. "So people just because they see blue skies should not think, 'Oh this storm is gone and the aftermath is over with.'"

In Washington, the federal government shut down for two days. Offices, monuments and subway tunnels were all but abandoned, frustrating tourists. Some were surprised that monuments and museums were closed Thursday, hours ahead of the storm.

"I think it's a little overkill," said Sandra de Dubovay, who was visiting from the Los Angeles area. "Some people only have a day here. It is frustrating."

With mid-Atlantic states left sodden by an unusually wet summer, the winds toppled trees and rains flooded creeks and low-lying areas.

In Middletown, N.J., Isabel sent a tree crashing through the roof of Jean Paul Zammit's house.

"It was a just a big bang and crack, and the ceiling falling down and everything falling down," said Zammit, who was sitting in his living room when the roof caved in.

At 8 a.m., Isabel was 25 miles east of Pittsburgh, moving northwest at around 22 mph.

Up to 5 1/2 inches of rain was possible in West Virginia, down from an original forecast of as much as a foot. One to 3 inches were forecast for parts of Pennsylvania.

In Virginia alone, more than 1.5 million people lost power by late Thursday and more than 16,000 people filled evacuation shelters. Six people were killed in a pair of weather-related traffic accidents in the state; two were killed by falling trees. One man drowned while canoeing.

"Virginians need to realize that they're in for a tough couple of days," said Gov. Mark R. Warner.

Some of the worst flooding on Thursday was along the Chesapeake Bay, where an 8.2-foot storm surge sent water into low-lying areas, particularly Norfolk and Portsmouth.

Along the York River in Gloucester County, authorities rescued eight people stranded on a small island surrounded by raging currents. Water around the island started to recede Thursday, lessening the danger to others who remained stranded.

The Potomac River was forecast to see a 5- to 6-foot surge by early Friday morning. Streets were flooded in Alexandria's colonial Old Town district in Virginia.

President Bush declared major disasters in North Carolina and Virginia, ordering federal aid to both states. The governors of Pennsylvania, West Virginia, Maryland, New Jersey and Delaware declared state emergencies.

Maryland Gov. Robert Ehrlich said flooding, whether from storm surges on the Eastern Shore or heavy rainfall, was "the No. 1 danger."

In Baltimore, the storm blew down three buildings that would have to be demolished and downed trees and utility lines. About 63,000 homes and businesses lost power, and 34 people were rescued, some by boat, from their homes in a neighborhood where waist-high water flooded some streets, Mayor Martin O'Malley said.

The storm knocked out generators at two water treatment plants and a sewage treatment plant in neighboring Anne Arundel County. County Executive Janet Owens urged residents to be patient and conserve water until power was restored.

"Putting it bluntly, please don't flush," Owens said. "It buys us some time."

The storm spared much of North Carolina the kind of flood damage is experienced from Hurricane Floyd in 1999. The storm flooded some low-lying areas and knocked out electricity for hundreds of thousands, but it didn't appear to pack the same destructive punch as Floyd, which left 56 dead and a wide swath of the state underwater.

On isolated Ocracoke Island along the Outer Banks, about 15 people gathered at Howard's Pub to ride out the storm.

"Isabel's eye passed right over us," said Buffy Warner, the pub's owner. "It was so dramatic. The rain was actually driving horizontally with these incredibly dark skies and no visibility. Then, within about 60 seconds, the sky became bright white."

A utility employee in North Carolina was electrocuted while restoring power. The other storm-related deaths were from falling trees or car accidents.

Well over 1,500 flights were canceled at airports in the major Eastern cities, said David Stempler, president of the Air Travelers Association. As the storm moved north, all flights to and from the Washington metropolitan area's airports were likely to be canceled, he said.

In Warren County, N.J., police evacuated 168 residents of a Salem County nursing home when water rose in the Delaware Bay around 3 a.m., state police said. Residents were taken to two local shelters.

ON THE NET

National Hurricane Center: http://www.nhc.noaa.gov/

WeatherFlow Inc. wind sensors: http://www.weatherflow.com/hatterasuscg