Hurricane Fiona strengthened to a powerful Category Four storm today as it headed toward Bermuda after carving a destructive path through the Dominican Republic and Puerto Rico, where most were without power and up to eight people might have died from the storm.

After making landfall in Puerto Rico on Sunday, Fiona caused devastating flooding and landslides on the island and gathered steam as it barreled into the Dominican Republic and the Turks and Caicos Islands over the next two days.

By today, Fiona was packing winds as high as 215 km per hour and was expected to strengthen as it moved north toward Bermuda, though the current forecast does not see Bermuda taking a direct hit, the National Hurricane Center said. It could reach Canada's eastern coast on Friday.

"On the forecast track, the center of Fiona will continue to move away from the Turks and Caicos today, approach Bermuda late on Thursday and approach Atlantic Canada late Friday," the agency said in an 11am ET update.

In Puerto Rico, where 40% of the island's 3.3 million residents were still without water and three-quarters were lacking power, authorities were trying to get a handle on the scale of the destruction and start rebuilding.

At least eight deaths are being investigated as potentially caused by Fiona, including a sick four-month-old infant whose mother struggled to get to the hospital due to blocked roads, Dr Maria Conte Miller, director of the Institute of Forensic Sciences, said in a roundtable yesterday.

The US Federal Emergency Management Agency has so far attributed four deaths to the storm in Puerto Rico. A fifth person was killed in Guadeloupe earlier in the week.

Businesses damaged after the passage of Hurricane Fiona, in Samana, Dominican Republic

For many Puerto Rico residents, the memory of the devastation from Hurricane Maria in 2017 is still fresh.

Some 3,000 people died in that Category Five storm, which left the entire island without electricity for a week.

Marylou Maldonado, 45, a saleswoman from the town of Camuy in northwestern Puerto Rico, said water was restored to her residence yesterday, but the governor and energy provider failed to fulfill their promise to restore power to her region.

"People are under a lot of stress," she said. "Here in this area, the crisis is emotional. It is emotional because of the frustration of not having electricity and that we are being lied to."

The Bermuda Weather Service has issued a tropical storm warning for the archipelago, which lies 966 km east of the US state of North Carolina, as Fiona tracks to the west of the British Overseas Territory.

Hurricane-force winds are a possibility depending on the storm's path, it said.

"Outer rain bands will sweep into the region bringing bouts of showers, thunderstorms, and heavy rain," the weather service said in its forecast for tomorrow and Friday.

An estimated 1.07 million homes and businesses remained without power in Puerto Rico by midday on Wednesday, according to LUMA Energy, which has said full restoration to all 1.5 million customers could take several days.

In the neighboring Dominican Republic, Fiona triggered severe flooding that limited road access to villages, forced 12,500 people from their homes and knocked out power to hundreds of thousands of people.

Fiona was the first hurricane to score a direct hit on the Dominican Republic since Jeanne left severe damage in the east of the country in 2004.

US Health Secretary Xavier Becerra declared a public health emergency for Puerto Rico on Tuesday night, freeing up federal funds and equipment to assist the island.

'I have food and water'

Meanwhile, US President Joe Biden dispatched the head of the Federal Emergency Management Agency to the island.

"We're sending hundreds of additional personnel to support all affected communities," FEMA Administrator Deanne Criswell said after a tour with Pedro Pierluisi, the island's governor.

Mr Pierluisi said the storm had caused catastrophic damage on the island of three million people since Sunday, with some areas receiving more than 76cm of rain.

Michelle Carlo, medical advisor for Direct Relief in Puerto Rico, told CBS News that "a lot of people in Puerto Rico are suffering right now."

"About 80% of Puerto Ricans are still without power and about 65% are without water service," Ms Carlo said.

Over one million people are still without electricity two days after
Hurricane Fiona struck this Caribbean nation

Across Puerto Rico, Fiona caused landslides, blocked roads and toppled trees, power lines and bridges, Mr Pierluisi said.

A man was killed as an indirect result of the power blackout - burned to death while trying to fill his generator, according to authorities.

On Monday afternoon, Nelly Marrero made her way back to her home in Toa Baja, in the north of Puerto Rico, to clear out the mud that surged inside after she evacuated.

"Thanks to God, I have food and water," Ms Marrero - who lost everything when Hurricane Maria devastated Puerto Rico - told AFP by telephone.