MIAMI, Florida - Hurricane Irma has strengthened into a Category 5 storm as it roared toward the northeast Caribbean on a path toward the U.S.

Irma's maximum sustained winds increased to 175 mph early Tuesday. It was centered about 270 miles east of Antigua and moving west at 14 mph.

States of emergency were declared in Puerto Rico, the U.S. Virgin Islands and all of Florida while people on various Caribbean islands boarded up homes and rushed to find last-minute supplies, forming long lines outside supermarkets and gas stations.

Irma was centered 320 miles east of the Leeward Islands and moving west at 14 mph, the hurricane center said.

Authorities warned that the storm could dump up to a foot of rain, cause landslides and dangerous flash floods and generate waves of up to 23 feet.

Residents on the U.S. East Coast were urged to monitor the storm's progress due to the possibility it could turn northward toward Florida, Georgia or the Carolinas.

People were shopping for gasoline, generators, food, batteries, and everything else they'd need get by were Irma to hit the region hard.

"We are not yet at the height of hurricane season and people have not taken steps to get prepared yet," Miami-Dade County Emergency Management Director Curt Sommerhoff said Monday. "We are encouraging them to take those steps today."

Miami-Dade officials were to meet Tuesday to assess the danger.

In the Caribbean, hurricane warnings were issued for 16 islands and island groups, including Antigua, where the governor urged people to evacuate the tiny island of Anegada if they could ahead of the storm.

Vivian Wheatley, proprietor of the Anegada Reef Hotel, planned to stay behind. She said she would stay in one of the hotel rooms and take advantage of the generator since there were no guests

"We know it's a very powerful (storm), and we know it's going to be very close," she said. "Let's hope for the best."

People in Puerto Rico, a U.S. territory, braced for electricity outages after the director of the island's power company predicted that storm damage could leave some areas without power for four to six months. But "some areas will have power (back) in less than a week," Ricardo Ramos told radio station Notiuno 630 AM. The utility's infrastructure has deteriorated greatly during a decade-long recession, and Puerto Ricans experienced an island-wide outage last year.

Both Puerto Rico and the U.S. Virgin Islands expected 4 inches to 8 inches of rain and winds of 40-50 mph with gusts of up to 60 mph.

The Associated Press contributed to this report.