Hurricane Gonzalo strengthened as it swirled in the northern Caribbean toward the British Virgin Islands overnight, the U.S. National Hurricane Service said.
Gonzalo's center is expected to pass just northeast of the British Virgin Islands in the early hours of Tuesday morning before heading into open Atlantic waters north of Puerto Rico, the service added.
Puerto Ricans stocked up on water, batteries and other emergency supplies, and emergency personnel were put on alert.
But most forecasts show it posing no threat to the mainland United States and moving still further north into the Atlantic.
On Monday, Gonzalo's heavy rains and high winds destroyed several fishing boats, blew off roofs and downed power lines in Antigua and Barbuda.
Antiguan Prime Minister Gaston Browne ordered schools closed for a national cleanup effort on Tuesday to get the nation "fully back in business'' by Wednesday.
Gonzalo was about 80 miles (130 km) northeast of St. Thomas in the U.S. Virgin Islands and packed sustained winds reaching nearly 105 miles per hour (165 km per hour) early on Tuesday, the service said.
It is forecast to strengthen for another two days and become a major hurricane within the next 24 hours, the service added.
Hurricane warnings were in effect for the British Virgin Islands as well as Anguilla early on Tuesday. A hurricane watch for Puerto Rico and the U.S. Virgin Islands was downgraded to a tropical storm warning.
Gonzalo is the sixth hurricane of the 2014 Atlantic hurricane season. Forecasters in August predicted lower than usual activity for the season, with seven to 12 named storms and no more than two reaching major hurricane status.
A major hurricane is considered to be Category 3 or above with winds hitting at least 111 mph (178 kph).