U.S. Homeland Security Secretary Janet Napolitano has cautioned people along the path of Tropical Storm Irene that even if the storm has passed their area, danger remains.
Napolitano said Sunday that downed power lines, flooding, generator problems and fallen trees are all potential threats once the storm is gone.
Even as Irene continues on a path up the coastline of the northeastern United States, the Homeland Security chief said damage assessment has begun in the southern states of North Carolina and Virginia.
A loss-estimate company, Eqecat, already has estimated the damage to North Carolina and Virginia at $200 to $400 million.
The National Hurricane Center says Irene has weakened since leaving the New York City area and is now traveling at about 40 kilometers an hour with maximum sustained winds of 95 kilometers an hour.
Forecasters say Irene will move into Canada by Sunday night. In areas where the storm already has passed, weather officials say the damage was not as severe as they feared it would be.
The storm has killed at least 15 people and paralyzed ground and air traffic in its journey up the eastern U.S. coast.
New Jersey Governor Chris Christie has predicted record-level flooding for parts of his coastal state, and Pennsylvania Governor Tom Corbett has warned that rivers in the affected areas of his state may not crest until Tuesday or Wednesday.
The White House says President Barack Obama has been briefed on the emergency response to the storm.
Irene was downgraded to a tropical storm as it approached New York City early Sunday, but it still managed to flood some streets and a traffic tunnel in lower Manhattan, as the East and Hudson Rivers rose with high tide.
The city has not said yet when it will restart the public transit system, which has been shut down as a safety precaution since midday Saturday.
Irene blasted ashore in North Carolina early Saturday, flooding streets and toppling trees with winds of 140 kilometer per hour. The storm later moved into the Washington, D.C. area, which was hit with strong winds, heavy rain, localized flooding and falling trees.
More than four million homes and businesses in the eastern U.S. lost power because of the storm, which is passing through some of the country's most densely populated areas. Suspected tornadoes spurned by the hurricane destroyed homes in Delaware and Virginia.