MIAMI >> Officials and residents from Florida to the Carolinas stocked up on supplies, dusted off evacuation plans and readied for the worst as Irene, the first hurricane to threaten the U.S. in three years, churned over tropical waters after cutting a destructive path through the Caribbean.

Federal officials warned the storm could flood streets and knock down power lines as far north as New England.

Hurricane Irene, which already has raked the Caribbean, could cause serious problems along the entire Eastern Seaboard, Federal Emergency Management Agency administrator Craig Fugate said Tuesday during a conference call with reporters. Fugate urged people not to become complacent, even though the forecast is still uncertain and the storm may be days from hitting the U.S.

"We need to remind people, hurricanes are not just a Southern thing. This could be the Mid-Atlantic and the northeast coast," Fugate said. "We’ve got a lot of time for people to get ready, but we don’t have forever."

Officials on North Carolina’s Okracoke Island — where Irene appeared to be taking dead aim as of Tuesday — were taking no chances. Tourists were ordered to evacuate Wednesday, while residents were told to be off the island by Thursday, said Tommy Hutcherson, who serves on the local board that issues such orders.

Hutcherson, who also owns the Ocracoke Variety Store, said authorities have to issue such orders early because of the limited capacity of the ferries. Still, that doesn’t mean everyone will leave.

"I’ll be here," said Hutcherson, a 29-year resident who has ridden out numerous past storms. "A lot of the locals will choose to stay."

The barrier island is only accessible by boat. It is 16 miles long and mostly undeveloped, with a town at the southern tip.

Caitlin Blue, who works at the Kure Beach Fishing Pier, said Tuesday employees were preparing to board up the windows.

"That’s really all you can do," said Blue, 17. "Everybody’s a little apprehensive, especially the owner of the pier. This one is supposed to come right down on us."

The Kure pier has been rebuilt twice after being destroyed by hurricanes — Hazel in 1954 and the double hit in 1996 from Bertha and Fran.

Many people already have begun stocking up on essentials such as bottled water, gasoline and plywood for boarding up windows.

It’s possible Irene will make landfall over the North Carolina coast, then move to the north into the Chesapeake Bay sometime Sunday. However, because such projections can be uncertain, it’s also possible Irene could straddle the coast.

Fugate and National Hurricane Center director Bill Read said Irene could cause problems even over open water. New England is particularly vulnerable to heavy rains because the soil is already saturated from summer storms, which could raise the threat of flash flooding.

If Irene does move into the Mid-Atlantic area, it could threaten plans for dedicating a memorial to Martin Luther King Jr. Fugate said officials were discussing whether to hold Sunday’s dedication ceremony. Tens of thousands are expected to attend the event at the National Mall in Washington, D.C.

Irene already has brought torrential rains, flooding and dangerous winds to the Caribbean.

The storm slashed directly across Puerto Rico, tearing up trees and knocking out power to more than a million people. It then headed out to sea, north of the Dominican Republic, where the powerful storm’s outer bands were buffeting the north coast with dangerous sea surge and downpours. President Barack Obama declared an emergency for Puerto Rico, making it eligible for federal help.

At least hundreds were displaced by flooding in the Dominican Republic, forced to take refuge in churches, schools or relatives’ homes. Electricity also was cut in some areas.

"Everything filled with water, there was just water everywhere," said Maria Altagracia Fernandez, who spent Monday night sleeping on the floor with her five children and about 100 other people at a shelter in the fishing town of Boba, 135 miles (225 kilometers) northeast of Santo Domingo.

Irene was forecast to pass over or near the Turks and Caicos Islands and the southeastern Bahamas by Tuesday night and be near the central Bahamas early Wednesday.

In the U.K. territory of the Turks and Caicos, a steady stream of customers bought plywood and nails at hardware stores, while others readied storm shutters and emergency kits at home.

The prime minister of the Bahamas, Hubert Ingraham, warned islanders that the combination of dangerous storm surge and torrential rains from Hurricane Irene will most likely lead to severe flooding in coastal and low-lying areas. He warned in a televised announcement that people in those areas should seek higher ground.

Ingraham said if Irene strengthens to a Category 3 hurricane, "damage to roofs and to weak structures can be expected." He urged islanders to prepare supplies of water, canned foods, flashlights, batteries and first aid kits and pick up debris that whipping winds could turn into dangerous projectiles.

"I ask the prayers of the clergy and others for the safety of the people of our Bahamas. We can, and will, replace and restore anything we may lose. We cannot replace life. Hence my urgent and repeated appeals for the observance of safety measures," Ingraham said.

In South Carolina, emergency agencies went on alert for what could be the first hurricane to hit there in seven years.

"This is potentially a very serious hurricane," longtime Charleston Mayor Joseph P. Riley Jr. said. He led Charleston’s recovery from the massive destruction of Hurricane Hugo’s 135 mph winds and waves back in 1989.

It’s been more than a century since Georgia has taken a direct hit from a Category 3 storm or greater. That was in 1893, and the last hurricane to make landfall along the state’s 100-mile coast was David, which caused only minor damage when it struck in 1979.

If Irene makes it as a major storm to New England, Read drew comparisons to a huge 1938 hurricane that also approached from the South and killed 682 people.

"We’re very concerned about what’s going to happen in New England," Read said.

Irene could bring much-needed relief to a fire blazing in the Great Dismal Swamp on the North Carolina-Virginia line, however. If the storm stays on its current track, it could soak the smoldering fire that’s consumed more than 9 square miles of swamp in both states.

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Associated Press writers Ezequiel Abiu Lopez in Nagua, Dominican Republic, Gary Fineout in Tallahassee, Martha Waggoner and Michael Biesecker in Raleigh, N.C., and Bruce Smith in Charleston, S.C., contributed to this report.