MIAMI (AP) — Hurricane Dorian posed an increasing menace to Florida as it pushed over open waters Thursday after leaving limited damage in Puerto Rico and the Virgin Islands.

The U.S. National Hurricane Center said Dorian was expected to grow into a potentially devastating Category 3 hurricane before hitting the U.S. mainland late Sunday or early Monday somewhere between the Florida Keys and southern Georgia.

Across much of Florida's east coast, residents began flocking to the grocery stores and gas stations, stocking up in anticipation of the storm. There were lines at many gas stations in South Florida as people began filling gas cans and topping off their gas tanks. Some residents using community Facebook groups gave updates on new shipments of water to restock the nearly empty shelves at local grocery stores.

Florida Gov. Ron DeSantis declared a state of emergency for the state's eastern and central counties Wednesday and planned to visit the National Hurricane Center in Miami on Thursday morning.

County governments along the state's central east coast distributed sandbags and many residents rushed to warehouse retailers to load up on water, canned food and emergency supplies.

"Hurricane Dorian looks like it will be hitting Florida late Sunday night," President Donald Trump tweeted Thursday morning. "Be prepared and please follow State and Federal instructions, it will be a very big Hurricane, perhaps one of the biggest!"

Dorian blew through the Virgin Islands as a Category 1 hurricane Wednesday while raking nearby Puerto Rico with high winds and rains.

The storm caused an islandwide blackout in St. Thomas and St. John in the U.S. Virgin Islands, and scattered power outages in St. Croix, government spokesman Richard Motta said. The storm also downed trees and at least one electric pole in St. Thomas, he said.

And there were no reports of serious damage in the British Virgin Islands, where Gov. Augustus Jaspert said crews were already clearing roads and inspecting infrastructure by late Wednesday afternoon.

Early Thursday, Dorian was centered about 150 miles north-northwest of San Juan, Puerto Rico. The U.S. National Hurricane Center said its top winds were blowing at 85 mph as the storm moved northwest at 13 mph.

The Hurricane Center projected the storm could have winds of 125 mph by the time it reaches the mainland. Also imperiled were the Bahamas, with Dorian's forecast track running just to the north of Great Abaco and Grand Bahama islands.

Puerto Rico seemed to be spared any heavy wind and rain, a huge relief on an island where blue tarps still cover some 30,000 homes nearly two years after Hurricane Maria. The island's 3.2 million inhabitants also depend on an unstable power grid that remains prone to outages since it was destroyed by Maria, a Category 4 storm.

Several hundred customers were without power across Puerto Rico, said Ángel Figueroa, president of a union that represents power workers.

Police said an 80-year-old man in the northern town of Bayamón died Wednesday after he fell trying to climb up to his roof to clear it of debris ahead of the storm.