Hurricane Ian severs section of Florida's Sanibel Causeway

(AP) — A chunk of the Sanibel Causeway in Florida 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.

A photo taken nearby shows a spiral staircase deposited in the brush next to a white pickup truck after the hurricane passed.

Hurricane Ian carved a path of destruction across Florida, trapping people in flooded homes, 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, drenching much of Florida and the southeastern Atlantic coast.

Rain and overflow from rivers are causing severe flooding near parts of Florida's Atlantic coast as storm Ian makes its way back out to sea, officials said Thursday.

The Daytona Beach region is experiencing “historic flooding" that includes water in people’s homes, Volusia County Sheriff Mike Chitwood said at a news conference. He implored people to stay off the roads, and the county has imposed a curfew until 7 a.m. Friday.

“This is unprecedented for Volusia County,” said local emergency management official Jim Judge.

Farther inland, residents of a nursing home were taken to ambulances and buses Thursday morning in an Orlando neighborhood that doesn’t typically flood.

Paramedics rolled Avante Orlando residents out on stretchers and wheelchairs. At a neighboring apartment complex, cars were submerged in the parking lot.

The Orange County Sheriff’s Office posted photos of deputies helping two people and a dog get to dry land north of Orlando.

South of Sanibel, towering waves destroyed the historic beachfront pier in Naples, tearing out even the pilings underneath. “Right now, there is no pier,” said Penny Taylor, a commissioner in Collier County, which includes Naples.

Emergency crews sawed through toppled trees to reach flooded homes, but with no electricity and virtually no cell service, it was impossible for many people to call for help when the surge filled their living rooms.

“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. “We can tell you as daylight reveals the aftermath, it’s going to be a hard day.”

In Fort Myers, Valerie Bartley was terrified as her family spent desperate hours holding a dining room table against their patio door as debris slammed into their house.

"We just assumed that it was tearing our house apart,” she said. As the storm raged outside, she said her 4-year-old daughter grabbed her hand and said: “I'm scared too, but it's going to be OK.”

Ian made landfall Wednesday near Cayo Costa, a barrier island just west of heavily populated Fort Myers, as a Category 4 hurricane with 150-mph winds, tying it for the fifth-strongest hurricane, when measured by wind speed, ever to strike the U.S.

Ian’s center came ashore more than 100 miles south of Tampa and St. Petersburg, sparing them their first direct hit by a major hurricane since 1921. Water drained from Tampa Bay as it approached, then returned with a surge.

The National Hurricane Center said Ian was expected to regain near-hurricane strength after emerging over Atlantic waters near the Kennedy Space Center, with South Carolina in its sights for a second U.S. landfall.

Meanwhile, a stretch of the state remained under as much as 10 feet of water Thursday morning, with destructive waves "ongoing along the southwest Florida coastline from Englewood to Bonita Beach, including Charlotte Harbor,” the center said.

In Port Charlotte, a hospital’s emergency room flooded and fierce winds ripped away part of the roof, sending water gushing down into the intensive care unit. The sickest patients -- some on ventilators — were crowded into the middle two floors as the staff prepared for storm victims to arrive, said Dr. Birgit Bodine of HCA Florida Fawcett Hospital.

The Florida Highway Patrol shut down the Florida Turnpike in the Orlando area due to significant flooding and said the main artery in the middle of the state will remain closed until the water subsides.

Calls from people trapped in flooded homes or from worried relatives flooded 911 lines. Pleas were also posted on social media sites, some with video showing debris-covered water sloshing toward the eaves of their homes.

Brittany Hailer, a journalist in Pittsburgh, contacted rescuers about her mother in North Fort Myers, whose home was swamped by 5 feet of water.

“We don’t know when the water’s going to go down. We don’t know how they’re going to leave, their cars are totaled,” Hailer said. “Her only way out is on a boat.”

Another boat, carrying Cuban migrants, sank Wednesday in stormy weather east of Key West.

The U.S. Coast Guard initiated a search and rescue mission for 23 people and managed to find three survivors about two miles south of the Florida Keys, officials said. Four other Cubans swam to Stock Island, just east of Key West, the U.S. Border Patrol said. Air crews continued to search for possibly 20 remaining migrants.

The storm previously killed two people in Cuba and brought down the country’s electrical grid.

More than 2.5 million Florida homes and businesses were left without electricity, according to the PowerOutage.us site. Most of the homes and businesses in 12 counties were without power.

Sheriff Bull Prummell of Charlotte County, just north of Fort Myers, announced a curfew between 9 p.m. and 6 a.m. “for life-saving purposes,” saying violators may face second-degree misdemeanor charges.

“I am enacting this curfew as a means of protecting the people and property of Charlotte County,” Prummell said.

At 8 a.m. Thursday, the storm was about 40 miles east of Orlando and 10 miles southwest of Cape Canaveral, carrying maximum sustained winds of 65 mph and moving toward the cape at 8 mph, the center said.

Up to a foot of rain was forecast for parts of Northeast Florida, coastal Georgia and the Lowcountry of South Carolina. As much as 6 inches could fall in southern Virginia as the storm moves inland over the Carolinas, and the center said landslides were possible in the southern Appalachian mountains.

The governors of South Carolina, North Carolina, Georgia and Virginia all preemptively declared states of emergency.