San Juan, Puerto Rico (CNN) Puerto Rico grappled with damages and deaths caused by Hurricane Maria on Friday as the storm hurtled across the Caribbean and slapped the Turks and Caicos Islands.

People in the northwest part of the island were urged to evacuate in the afternoon after a dam on the Guajataca River failed, according to a tweet from the National Weather Service.

A gradual weakening of Maria is forecast over the next two days, but the Category 3 hurricane still socked the Turks and Caicos, a British overseas territory of more than 52,000 people.

Maria's core left the Turks and Caicos in a north-northwestward direction and was gradually moving away from the Bahamas, the center said in its 8 p.m. advisory.

A dangerous storm surge and large waves will raise water levels by as much as 9 to 12 feet above normal tide in the Turks and Caicos and southeastern Bahamas, the center said.

More rain and flash flooding in Puerto Rico

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The giant storm's death toll continues to mount.

At least 15 people are confirmed dead on Dominica, and dozens more remain missing. One person died in the US Virgin Islands, probably from drowning, authorities said.

At least six people were killed in Puerto Rico, said Héctor M. Pesquera, the island's public safety director.

Earlier, Puerto Rico's governor told CNN's "New Day" that 13 people had died in the storm. The figure was based on reports from mayors on the island, but law enforcement hasn't confirmed that total, the government said.

"Flash flooding continues in portions of Puerto Rico and the Dominican Republic due to persistent heavy rainfall from Maria's trailing rain bands," the hurricane center said.

The rain could spur "life-threatening flash floods and mudslides."

Hurricane Maria leaves a house destroyed in the Turks and Caicos Islands.

Maria is producing winds of near 125 mph (more than 200 kilometers per hour) with higher gusts. Moving at 9 mph (15 kilometers per hour), it was 375 miles (600 kilometers) east-southeast of Nassau, Bahamas.

The government of the Bahamas changed the hurricane warning for the Turks and Caicos Islands and the southeastern Bahamas to a tropical storm warning, the weather service said. A tropical storm warning is in effect for the central Bahamas.

Heavy rainfall is expected through Saturday. In Turks and Caicos, 8 to 16 inches are predicted, with 20 inches in some places, and in Puerto Rico, an additional 3 to 6 inches is likely, with isolated maximum storm totals at 40 inches.

Heavy rains are expected in parts of the Dominican Republic, Haiti and the Bahamas.

US Southeast coast to begin feeling impact

Maria will move closer to the US East Coast and Bermuda by the middle of next week, "but it is too soon to determine, what, if any direct impacts there might be in these areas," the hurricane center said.

Swells from the storm are expected to begin reaching the US Southeast coast, the center said.

"These swells are likely to cause dangerous surf and life-threatening rip currents along the coast for the next several days, even with Maria forecast to remain well offshore over the western Atlantic Ocean," it said.

Photos: Hurricane Maria slams the Caribbean An apartment building is missing a wall in San Juan, Puerto Rico, on Monday, September 25, nearly a week after Hurricane Maria devastated the US commonwealth. Power is still out in most places, and communications remain almost nonexistent on the island of 3.4 million people. Hide Caption 1 of 36 Photos: Hurricane Maria slams the Caribbean Yancy Leon rests at the Luis Muñoz Marin International Airport near San Juan on September 25. She's been waiting in line for two days to get a flight out. Hide Caption 2 of 36 Photos: Hurricane Maria slams the Caribbean An aerial view shows the flooding in San Juan on September 25. Hide Caption 3 of 36 Photos: Hurricane Maria slams the Caribbean People collect water from a natural spring created by landslides in Corozal, Puerto Rico, on Sunday, September 24. Puerto Rican Gov. Ricardo Rosselló said the island faces a humanitarian crisis. Hide Caption 4 of 36 Photos: Hurricane Maria slams the Caribbean An aerial view shows a flooded neighborhood in Catano, Puerto Rico, on Friday, September 22. Hide Caption 5 of 36 Photos: Hurricane Maria slams the Caribbean A man cleans a muddy street in Toa Baja, Puerto Rico, on September 22. Hide Caption 6 of 36 Photos: Hurricane Maria slams the Caribbean A man walks on a highway divider while carrying his bicycle through San Juan, Puerto Rico, on Thursday, September 21. Hide Caption 7 of 36 Photos: Hurricane Maria slams the Caribbean A shack is destroyed in San Juan on September 21. Hide Caption 8 of 36 Photos: Hurricane Maria slams the Caribbean A gas station's sign is damaged in Punta Cana, Dominican Republic, as the hurricane passed just north of the country on September 21. Hide Caption 9 of 36 Photos: Hurricane Maria slams the Caribbean Rescue workers drive through a flooded road in Humacao, Puerto Rico, on Wednesday, September 20. Hide Caption 10 of 36 Photos: Hurricane Maria slams the Caribbean A mattress that fell from the third floor is surrounded by debris outside a San Juan apartment complex on September 20. Hide Caption 11 of 36 Photos: Hurricane Maria slams the Caribbean Damage is seen in Roseau, Dominica, on September 20. Hide Caption 12 of 36 Photos: Hurricane Maria slams the Caribbean People walk through the destruction in Roseau on September 20. Hide Caption 13 of 36 Photos: Hurricane Maria slams the Caribbean San Juan is shrouded in darkness after the hurricane knocked out power to the entire island of Puerto Rico. Hide Caption 14 of 36 Photos: Hurricane Maria slams the Caribbean Power lines are scattered across a road in Humacao, Puerto Rico, on September 20. Hide Caption 15 of 36 Photos: Hurricane Maria slams the Caribbean Residents move aluminum panels from an intersection in Humacao on September 20. Hide Caption 16 of 36 Photos: Hurricane Maria slams the Caribbean Rescue vehicles are trapped under an awning in Humacao on September 20. Hide Caption 17 of 36 Photos: Hurricane Maria slams the Caribbean Trees are toppled outside the Roberto Clemente Coliseum in San Juan on September 20. Hide Caption 18 of 36 Photos: Hurricane Maria slams the Caribbean Members of a rescue team embrace as they wait to help in Humacao on September 20. Hide Caption 19 of 36 Photos: Hurricane Maria slams the Caribbean A tree is damaged in Fajardo, Puerto Rico, on September 20. Hide Caption 20 of 36 Photos: Hurricane Maria slams the Caribbean Debris is strewn across a Fajardo street on September 20. Hide Caption 21 of 36 Photos: Hurricane Maria slams the Caribbean A woman closes her property in Naguabo, Puerto Rico, hours before Maria's arrival. Hide Caption 22 of 36 Photos: Hurricane Maria slams the Caribbean People take shelter at Puerto Rico's Humacao Arena on Tuesday, September 19. Hide Caption 23 of 36 Photos: Hurricane Maria slams the Caribbean Two girls play on cots at the Humacao Arena. Hide Caption 24 of 36 Photos: Hurricane Maria slams the Caribbean Waves crash in San Juan as the hurricane neared Puerto Rico on September 19. Hide Caption 25 of 36 Photos: Hurricane Maria slams the Caribbean People pray in Humacao on September 19. Hide Caption 26 of 36 Photos: Hurricane Maria slams the Caribbean A street is flooded in Pointe-a-Pitre, on the French Caribbean island of Guadeloupe, on September 19. Hide Caption 27 of 36 Photos: Hurricane Maria slams the Caribbean People stand near debris at a restaurant in Le Carbet, Martinique, on September 19. Hide Caption 28 of 36 Photos: Hurricane Maria slams the Caribbean People in Luquillo, Puerto Rico, board up windows of a business on September 19. Hide Caption 29 of 36 Photos: Hurricane Maria slams the Caribbean A boat is overturned off the shore of Sainte-Anne, Guadeloupe, on September 19. Hide Caption 30 of 36 Photos: Hurricane Maria slams the Caribbean Cars line up at a gas station in San Juan on September 19. Hide Caption 31 of 36 Photos: Hurricane Maria slams the Caribbean A motorist drives on the flooded waterfront in Fort-de-France, Martinique, on September 19. Hide Caption 32 of 36 Photos: Hurricane Maria slams the Caribbean Floodwaters surround cars in Pointe-a-Pitre on September 19. Hide Caption 33 of 36 Photos: Hurricane Maria slams the Caribbean Soldiers patrol a street in Marigot, St. Martin, as preparations were made for Maria on September 19. Hide Caption 34 of 36 Photos: Hurricane Maria slams the Caribbean People buy provisions in Petit-Bourg, Guadeloupe, as the hurricane approached on Monday, September 18. Hide Caption 35 of 36 Photos: Hurricane Maria slams the Caribbean Customers wait in line for power generators at a store in San Juan on September 18. Hide Caption 36 of 36

Death, destruction

Parts of the Caribbean that Maria has already struck are just coming to terms with the extent of their losses.

CNN's Michael Holmes, who is on Dominica, said that almost all trees from the lush paradise have been denuded, leaving a stark, brown landscape in its place.

Aid had been stockpiled before Hurricane Irma, the storm that recently preceded Maria, but it was distributed to neighboring islands after Dominica appeared to have avoided the worst of it. Then came Maria.

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In Puerto Rico, every inch of the island was hammered when Maria made landfall Wednesday.

As many as 4,500 Army reservists have been brought in to complement the Puerto Rican National Guard, says Brig. Gen. Dustin Shultz, who is commanding the reserves in the Caribbean during rescue effort.

Gov. Kenneth E. Mapp of the US Virgin Islands is calling for "all hands on deck" as the territory expands recovery efforts after both Irma and Maria struck in less than two weeks.

The Royal Navy's flagship HMS Ocean arrived in the British Virgin Islands with about 650 personnel and 60 tons of cargo, including construction equipment, hygiene kits and water purification tablets. The ship's arrival means there are now more than 2,000 UK military personnel working on relief.

US President Donald Trump has pledged federal help for Puerto Rico and the US Virgin Islands.

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Tough conditions in hospital

In San Juan, Ashford Presbyterian Community Hospital suffered damage. It's part of life in the "hurricane corridor," hospital planning director Margo Silva told CNN.

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"We're used to dealing with this. Unfortunately, being so close to the ocean, these circumstances come up," Silva said

She's been at the hospital for two months, and her daughter Jacqueline Alarondo was distressed. Water only arrived Thursday afternoon, she said. "It was bad, messed-up organization from the administration."

But another patient, Ana Rivera, said it might have been the best place to ride out the storm. The food comes on time, and they've been treating her well, she said.

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Ten miles west of the capital, residents trudged through floodwaters to reach their homes -- many of which no longer had roofs.

Sylvia Colon fought back tears as firefighters and the National Guard reached her 84-year-old neighbor. She refused to leave the woman who, she says, is like a grandmother to her.

One girl, Marytere, 16. had to cross floods with her family, clutching small dogs, along with bags filled with food, toiletries and pillows, to reach the rescue team.

The family had left to find help when the water got too high. "I'm scared of what's going to happen now to us," she said, wiping away tears.

"What's the family going to do now?"