Emergency crews have worked to reach stranded Florida residents as Hurricane Ian trained its sights on the Carolinas after cutting a coast-to-coast path of destruction across Florida, leaving behind deadly floodwaters, downed power lines and widespread damage.

Ian, one of the strongest storms ever to hit the US mainland, flooded Gulf Coast communities and knocked out power to millions before plowing across the peninsula to the Atlantic Ocean, where it regained strength before another anticipated landfall in South Carolina on Friday.

Florida’s death toll remained uncertain amid scattered reports of casualties.

President Joe Biden, speaking at Federal Emergency Management Agency (FEMA) headquarters in Washington, said Ian could prove to be the deadliest in state history.

“The numbers are still unclear, but we’re hearing early reports of what may be substantial loss of life,” Biden said on Thursday.

In hard-hit Charlotte County, a spokesperson for the sheriff’s department confirmed multiple deaths but did not have a firm figure. Authorities in Sarasota County were investigating two possible storm-related deaths, a sheriff’s spokesperson said.

A 72-year-old man in Deltona in central Florida died after he went outside during the storm to drain his pool, authorities said.

More than 2.6 million homes and businesses in Florida remained without power. Governor Ron DeSantis said that Lee and Charlotte counties, home to more than 900,000 people, were “basically off the grid”.

Georgia, South Carolina and North Carolina were bracing for impact as Ian – which weakened to a tropical storm during its trek across Florida – returned to hurricane strength by late Thursday afternoon after moving into the Atlantic Ocean, with maximum sustained wind speeds of 120km/h, the US National Hurricane Center said.

The storm was expected to make landfall again early on Friday afternoon just north of Charleston. A hurricane warning was in effect for about 370km of coastline from the South Carolina-Georgia border north to Cape Fear, North Carolina.

In South Carolina, Mercedes Benz, Boeing Co and the seaports that support manufacturers will suspend operations on Friday.

The coastal city of Savannah, Georgia, could see tropical storm force winds starting later Thursday or early Friday. Ian was expected to bring potential life-threatening storm surges and possible tornadoes to the region on Friday, the National Weather Service said.

North Carolina Governor Roy Cooper urged residents to “take necessary precautions”, warning of possible flooding, landslides and tornadoes.

“This storm is still dangerous,” Cooper said.

Ian blasted ashore in Florida at the barrier island of Cayo Costa on Wednesday afternoon as a category four hurricane with maximum sustained winds of 241km/h.

The storm transformed Florida’s southwestern shoreline, dotted with sandy beaches, coastal towns and mobile home parks, into a disaster zone as Ian swept seawater into waterfront homes.

“Sanibel Island is destruction … it got hit with really biblical storm surge. It washed away roads. It washed away structures,” DeSantis said during a news briefing as he described the damage to the popular vacation destination.

He said earlier that 28 helicopters were performing water rescues and the bridge to the island was impassable.

By midday on Thursday, residents in hard-hit areas such as Venice, in Sarasota County about 120km south of Tampa, hunted for family and friends while rescue crews worked to reach people trapped in flooded homes.

Biden spoke to DeSantis on Thursday, and FEMA director Deanne Criswell will be in Florida on Friday. Biden said he would travel to the state when conditions allowed.

He also approved a disaster declaration, making federal resources available to the counties affected by the storm.

-REUTERS