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Anxious Florida residents raided grocery store shelves and North Carolina called for the evacuation of three barrier islands as Hurricane Matthew — the most powerful Atlantic storm in about a decade — threatened to rake a large swath of the East Coast in the coming days.

The storm roared across the Caribbean on Tuesday, slamming into the western part of Haiti. While it's too soon to know if it will make a direct hit on Florida or somewhere else along the U.S. coast, Matthew is expected to create dangerous conditions. A hurricane watch was in place for parts of Florida, which was already seeing rain bands from the storm.

Simone Corrado and her husband tried to buy water at a Publix in their hometown of Davie, about 20 minutes from Miami Beach, and mostly found empty shelves. They were worried the roof of their garden-style apartment would leak during heavy rain.

"I got scared because all that was left at Publix was just the pricey water," Corrado said. "They really put the fear into you here. On the television screen every few minutes is the 'beep, beep, beep' storm alert."

Florida Gov. Rick Scott met with emergency officials along the coast, starting out in the Keys and traveling north. At a news conference in Daytona Beach, he noted that the storm's predicted path can change quickly and warned people to be ready.

"We can rebuild your home, we can rebuild your business. We can't rebuild your life," Scott said.

The dangerous Category 4 storm blew ashore around dawn in a corner of Haiti where many people live along the coast in shacks of wood or simple concrete blocks. At least seven people have died from Matthew's march through the Caribbean. The storm was headed north over the Bahamas and expected to brush the Florida coast.

A tropical storm watch was issued from Seven Mile Bridge in the Florida Keys to Deerfield Beach, north of Fort Lauderdale. A hurricane watch is in place further north.

"We are preparing for the worst, hoping for the best and not taking any chances," Scott said as he visited with emergency management officials in the Florida Keys.

The governor urged residents along the Interstate 95 corridor to start making preparations, which include having at least a three-day supply of water, food and medicine. He also asked residents to comply with any evacuation orders from local officials as the week progresses.

"Make sure you have a fully charged cellphone," Scott said. "If we lose power, you cannot charge your cellphones."

Scott noted that many people have moved to South Florida since Hurricane Wilma hit as a Category 3 storm in 2005. Matthew briefly reached the top classification, Category 5, becoming the strongest hurricane in the region since Felix in 2007.

Officials in Georgia and the Carolinas were also making preparations. At Cape Lookout National Seashore in North Carolina, superintendent Patrick Kenney said more than 100 trucks are being taken off the island and about 45 cabins are being cleared.

Ferry operators told Kenney it will take two days to evacuate everyone, meaning the islands should be empty sometime Wednesday.

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Associated Press writer Jennifer Kay in Miami Beach and Martha Waggoner in Raleigh, North Carolina, contributed to this report.