Hurricane Ian left a path of destruction in southwest Florida, trapping people in flooded homes, cutting off the only bridge to a barrier island, and knocking out power to 2.5 million people as it dumped rain across the peninsula on Thursday.

One of the strongest hurricanes to ever hit the US threatened catastrophic flooding around the state.

Ian’s tropical storm-force winds extended outward up to 665km, drenching much of Florida and the southeastern Atlantic coast.

Authorities confirmed at least one storm death in Florida.

A 72-year-old man was found dead early on Thursday in water in a canal behind his home in Deltona near Daytona Beach, the Volusia County Sheriff’s Office said in a statement. It said he appeared to be using a hose to drain his pool into the wide canal and fell down an incline that was “extremely soft and slippery due to the heavy rain”.

Another Florida sheriff said he believed the death toll would be “in the hundreds.” Lee County Sheriff Carmine Marceno told ABC’s Good Morning America that his office was receiving thousands of 911 calls from people needing rescue in the county that includes Fort Myers, but roadways were still impassable and bridges are compromised.

“It crushed us,” Marceno said. “We still cannot access many of the people that are in need.”

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 the 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.”

In Lee County, which includes Fort Myers, just south of where Hurricane Ian made landfall, the sheriff’s office posted a phone number family and friends can call for welfare checks, and said “If the line is busy, keep trying.”

Officials in nearby FortMyers received calls from people trapped in flooded homes or from worried relatives. Pleas were also posted on social media sites, some with videos showing debris-covered water sloshing toward the eaves of their homes.

Brittany Hailer in Pittsburgh contacted rescuers about her mother in FortMyers, whose home was swamped by water. “We don’t know when the water’s going to go down. We don’t know how they’re going to leave,” Hailer said. “Her only way out is on a boat.”