ST PETERSBURG, Florida (AP) — Hurricane Ian carved a path of destruction across Florida, trapping people in flooded homes, cutting off the only bridge to a barrier island, destroying a historic waterfront pier and knocking out power to 2.5 million people as it dumped rain over a huge area on Thursday.

Catastrophic flooding was threatened around the state as one of the strongest hurricanes to ever hit the United States crossed the peninsula. Ian's tropical-storm-force winds extended outward up to 415 miles (665 km), drenching much of Florida and the southeastern Atlantic coast.

"It crushed us," Lee County Sheriff Carmine Marceno told ABC's "Good Morning America." He said roads and bridges remained impassable, stranding thousands in the county where Ian made landfall just north of Fort Myers. "We still cannot access many of the people that are in need."

Authorities confirmed at least one storm death in Florida — a 72-year-old man in Deltona who fell into a canal while using a hose to drain his pool in the heavy rain, the Volusia County Sheriff's Office said. Another person died in Cuba after Ian struck there.

Marceno said that while he lacked any details, he believed the death toll would be "in the hundreds." Governor Ron DeSantis later said that toll was not confirmed and was likely an estimate based on 911 calls.

Fort Myers Mayor Kevin Anderson told NBC's "Today" that he had not been told of any deaths in the city, but Ian by far is the worst storm he's witnessed since the 1970s.

"Watching the water from my condo in the heart of downtown, watching that water rise and just flood out all the stores on the first floor, it was heartbreaking," Anderson said.

A chunk of the Sanibel Causeway fell into the sea, cutting off access to the barrier island where 6,300 people normally live. How many heeded mandatory evacuation orders before the storm surge washed over the island wasn't known.

Emergency crews sawed through toppled trees to reach people in flooded homes, but with no electricity and virtually no cell service, it was impossible for many people to call for help from the hardest hit coastal areas where the surge came in.

"Portable towers are on the way for cell service. Chances are your loved ones do not have ability to contact you," said the sheriff's office in Collier County, which includes Naples. "We can tell you as daylight reveals the aftermath, it's going to be a hard day."

Hurricane Ian turned streets into rivers and blew down trees as it slammed into southwest Florida on Wednesday with 150 mph (241 kph) winds. Ian's strength at landfall was Category four, tying it for the fifth-strongest hurricane, when measured by wind speed, ever to strike the US.

Ian's centre came ashore more than 100 miles (160 kilometres) south of Tampa and St Petersburg, sparing the densely populated Tampa Bay area from its first direct hit by a major hurricane since 1921.

The National Hurricane Center said Ian became a tropical storm over land early Thursday and was expected to regain near-hurricane strength after emerging over Atlantic waters near the Kennedy Space Center later in the day, with South Carolina in its sights for a second US landfall.