US President Barack Obama has officially declared the floods caused by Tropical Storm Irene in North Carolina and New York a disaster. The move allows the two states to tap federal funds for relief efforts. However, the declaration does not include Vermont, which suffered its worst flooding in decades. About 40 people in the US were killed by the storm, which also caused damage estimated at more than $10bn (£6.5bn) and forced a shutdown of New York City. Millions of people on the US east coast are still without power after Irene, which made landfall in the US on Saturday. It swept up the heavily populated eastern seaboard from North Carolina. By the time it reached New York, it had been downgraded from a hurricane to a tropical storm. Nonetheless, the New York subway system was closed for the first time in its history because of a natural disaster, while 370,000 people living in low-lying areas were ordered to leave their homes. In Vermont on Tuesday night, more than 200 roads were blocked or have been washed away, hampering rescue efforts to as many as 13 towns. National Guard troops flew in food, water and other emergency supplies to cut-off areas in the rural, mountainous state. They also brought in some provisions by road, using heavy-duty lorries. Irene had been expected to bring the most havoc to coastal areas, but some of its worst destruction took place far inland. New Jersey and upstate New York have also been badly affected as the rain from Irene swells rivers and flows south.