Photo: The Canadian Press

Hurricane damage in Mexico Beach, Fla. 

The devastation inflicted by Hurricane Michael came into focus Thursday with rows upon rows of homes found smashed to pieces, and rescue crews began making their way into the stricken areas in hopes of accounting for hundreds of people who may have stayed behind.

At least three deaths were blamed on Michael, the most powerful hurricane to hit the continental U.S. in over 50 years, and it wasn't done yet: Though reduced to a tropical storm, it brought flash flooding to North Carolina and Virginia, soaking areas still recovering from Hurricane Florence.

Under a perfectly clear blue sky, families living along the Florida Panhandle emerged from darkened shelters and hotels to a perilous landscape of shattered homes and shopping centres, beeping security alarms, wailing sirens and hovering helicopters.

Gov. Rick Scott said the Panhandle woke up to "unimaginable destruction."

"So many lives have been changed forever. So many families have lost everything," he said.

The full extent of Michael's fury was only slowly becoming clear, with some of the hardest-hit areas difficult to reach because of roads blocked by debris or water. 

Some of the worst damage was in Mexico Beach, where the hurricane crashed ashore Wednesday as a Category 4 monster with 155 mph (250 km/h) winds and a storm surge of nine feet. 

Entire blocks of homes near the beach were obliterated, reduced to nothing but concrete slabs in the sand. Rows and rows of other homes were turned into piles of splintered lumber or were crumpled and slumped at odd angles. Entire roofs were torn away and dropped onto a road.

State officials said 285 people in Mexico Beach had defied a mandatory evacuation order ahead of the storm.

National Guard troops made their way into the ground-zero town and found 20 survivors Wednesday night, and more rescue crews were pushing into the area, with the fate of many residents unknown.

As thousands of National Guard troops, law enforcement officers and medical teams fanned out, the governor pleaded with people in the devastated areas to stay away for now because of hazards that included fallen trees and power lines.

"I know you just want to go home. You want to check on things and begin the recovery process," Scott said. But "we have to make sure things are safe."

Over 900,000 homes and businesses in Florida, Alabama, Georgia and the Carolinas were without power.

The Coast Guard said it rescued at least 27 people before and after the hurricane came ashore, mostly from homes along the Florida coastline, and searched for more victims.

Among those brought to safety were nine people rescued by helicopter from a bathroom of their home in hard-hit Panama City after their roof collapsed, Petty Officer 3rd Class Ronald Hodges said.

In Panama City, most homes were still standing, but no property was left undamaged. Downed power lines lay nearly everywhere. Roofs had been peeled off and carried away. Aluminum siding was shredded to ribbons. Homes were split open by fallen trees.

Hundreds of cars had broken windows. Twisted street signs lay on the ground. Pine trees were stripped and snapped off about 20 feet high.

In nearby Panama City Beach, Bay County Sheriff Tommy Ford reported widespread looting of homes and businesses. He imposed a curfew and asked for 50 members of the National Guard for protection.