SAN JUAN, Puerto Rico – Raging floodwaters from Tropical Storm Otto overturned cars, toppled power lines  and washed out roads in the northeastern Caribbean, officials said Thursday, as high seas stalled efforts to free a grounded oil tanker.

The British Virgin Islands has been hit with the worst flooding in the territory's history, prompting the government to declare a state of emergency, according to Sharleen Dabreo, director of the Department of Disaster Management.

The rush of water downed utility lines, broke underground drainage pipes and flipped cars that remain mired in mud.

"It's almost like a river stripped through the center of Road Town," said Gov. William Boyd McCleary, who told The Associated Press that nearly 20 inches (51 centimeters) of rain have fallen since Tuesday.

"We've got a pretty serious situation here," McCleary said. "We're not out of the woods yet."

Dozens of people were without power and water Thursday afternoon, with most of the damage reported in Road Town, the British Virgin Islands capital, and elsewhere on the island of Tortola. Schools will remain closed until Monday, but government offices will reopen on Friday, McCleary said.

Officials also closed schools in the U.S. Virgin Islands and in St. Kitts and Nevis, where government spokesman Erasmus Williams said rough waters were still frustrating efforts to free an oil tanker that broke free of its moorings and ran aground in the capital's harbor Monday.

None of the roughly 18,000 barrels of diesel fuel inside the Turkish-flagged Azra-S have spilled.

In Puerto Rico, floods, landslides and uprooted trees forced the closure of dozens of roads, said Doris Torres, Department of Transportation spokeswoman.

An estimated 100 homes were flooded in St. Lucia, and a fishing village on the island's east coast was declared a disaster zone.

The U.S. National Hurricane Center in Miami said Otto became a tropical storm early Thursday and had maximum sustained winds near 60 mph (95 kph) in the afternoon. It was expected to grow into at least a minimum-force hurricane with winds of 75 mph (120 kph) by Friday night or Saturday.

Otto was centered about 280 miles (455 kilometers) northeast of Grand Turk Island and moving northeast, away from Caribbean islands, at about 6 mph (9 kph). The Hurricane Center predicted the storm will advance across the open Atlantic toward the Azores archipelago off Portugal.