Hurricane Michael left “unimaginable destruction” as it ploughed into coastal areas of Florida, the state’s governor, Rick Scott says.
“So many lives have been changed forever,” he said. “So many families have lost everything.”
The worst hit areas of Florida’s northwest coast saw houses ripped from their foundations, trees felled, and power lines strewn across streets.
Hurricane Michael struck on Wednesday with winds of 155mph (250km/h).
It weakened to a storm as it moved inland towards the north-east, but at least six people have died, most of them in Florida.
More than 370,000 people in Florida were ordered to evacuate but officials believe many ignored the warning.
Governor Scott said the US Coast Guard carried out 10 missions overnight, saving at least 27 people.
Which areas are worst affected?
Michael ploughed into Florida’s Panhandle coast near the town of Mexico Beach at 14:00 (18:00 GMT) on Wednesday, one of the strongest storms to ever hit the US mainland.
Ranked four on the five-step Saffir-Simpson scale and with a storm surge of 9ft (2.7m), it lifted homes from their foundations and heavily damaged others in districts closest to the sea in Mexico Beach, CNN helicopter footage showed.
Twenty survivors were found in the town overnight, AP reports, but 285 had refused to obey warnings to evacuate.
Head of the Federal Emergency Management Agency, Brock Long, called Mexico Beach “ground zero” due to the damage.
Trees were downed in Panama City, northwest of Mexico Beach, buildings flattened, boats and electrical cables scattered.
Apalachicola, with 2,300 residents, was also badly affected, the mayor reporting that downed cables were making it difficult to get through the town.
Debris and floodwater are also making some of the worst-hit areas difficult to reach.
Governor Scott urged residents not to return until the authorities “make sure things are safe”, given the danger from power lines and other debris.