Rescuers were on Friday surveying the damage after the most powerful storm to hit the Florida Panhandle in recorded history killed at least seven people. Michael flattened homes, plunged communities into darkness and ravaged whole neighborhoods.

"This hurricane was an absolute monster," Florida Gov. Rick Scott said Thursday. "And the damage left in its wake is still yet to be fully understood."

Officials warned that the number of dead was likely to rise as search crews struggled to gain access to ravaged areas and sift through the piles of debris.

Michael is not a spent force. The National Hurricane Center on Friday warned the storm was gaining strength with wind speeds reaching 65 mph and that it would remain dangerous as it moves off toward the Atlantic Ocean through the weekend.

Tropical storm-force winds extended as far as 275 miles from the center and flash flooding is still a risk for parts of the Carolinas and the southern mid-Atlantic.

Mike McAuliffe, 30, stayed in Panama City Beach with his wife, Rebecca, 33, during the storm.

"It's easily the scariest thing I've ever lived through," McAuliffe said in an interview. The couple were assessing damage and trying to help neighbors on Thursday.

Rebecca McAuliffe said: "You can't even recognize some of the areas in town."

Michael made landfall in Mexico Beach, Florida, on Wednesday just shy of Category 5 hurricane strength, with winds gusting at 155 mph. While the storm weakened through the night as it passed over Georgia, it still proved deadly.

Almost one-and-a-half million customers were without power from Florida to Virginia on Thursday night.

The damage could be particularly severe for the Carolinas, which are still cleaning up from Hurricane Florence.

"We need people in South Carolina and North Carolina to remain vigilant and be careful. This is a strong tropical storm pushing through," Brock Long, administrator of the Federal Emergency Management Agency, said on "Today."

Sharon Black, who lives in Wilmington, North Carolina, worried that Michael's winds would blow away debris still piled up on front lawns from Florence.

"I spent three or four weeks trying to take care of things" after Florence, Black said, adding that she hoped this storm would take it easy on the Carolinas.

North Carolina Gov. Roy Cooper said 6 inches of rain had fallen in parts of the state, triggering a mudslide in McDowell County, 100 miles west of Charlotte.

A man was killed when a tree fell on a residence in Greensboro, Florida, Sgt. Anglie Hightower, a spokeswoman for the Gadsden County Sheriff's Office, told NBC News. Three other people in Gadsden were killed in separate storm-related incidents, Hightower said.

Another man was killed in Iredell County, North Carolina, north of Charlotte, when a tree fell on his car, said Cooper, who blamed the incident on the storm. NBC affiliate WCNC of Charlotte reported that the death happened Thursday on Mocksville Highway in the town of Chambersburg. Officials didn't say whether anyone else was in the car.

An 11-year-old girl was killed near Lake Seminole, Georgia, when a metal carport used for boats was picked up by wind, crashed through the roof of a house and struck her in the head, said Travis Brooks, director of emergency management for Seminole County. The emergency call came in on Wednesday afternoon, but responders weren't able to get to the home until early Thursday because "the roads were so messed up," Brooks said.

A Virginia man was found dead after getting swept away from his car in Pittsylvania County, state police said Friday. James E. King Jr., 45, got caught in a flash flood around 3:30 p.m. Thursday and authorities discovered his body about seven hours later, police said.

Long said that crews were able to get to some hard-hit areas in the Florida Panhandle on Wednesday night but that getting to Mexico Beach, Apalachicola and Panama City Beach was deeply challenging because of damaged bridges leading to those areas.

The Coast Guard said shallow water response crews had rescued about 40 people, in addition to having helped evacuate 142 nursing home patients to a hospital in Pensacola. Scott, meanwhile, said 20 people were rescued uninjured from Mexico Beach overnight.

Scott urged residents to stay inside so search-and-rescue teams could get through, adding that many roads were impassable anyway. "You will not be able to get home if you live in or near the coast," he said.

An 80-mile stretch of Interstate 10, which weaves through the Panhandle, was closed Thursday so crews could clear debris, the Florida Highway Patrol said. Northeast, in Tallahassee, many more roads were closed, and 90 percent of the city was without power.

Two hospitals in Panama City were closed, but two temporary facilities opened to receive their patients and other people injured by the storm.

At Scott's request, President Donald Trump signed a major disaster declaration on Thursday.

The president told reporters that those affected by the storm were in his prayers, and he said the administration "will not rest or waver" until recovery was complete.

"The only thing we can say about Michael with certainty is that it was so fast. It went through like a bullet, but it was a devastating bullet," Trump said.

While many parts of the Panhandle remained inaccessible on Thursday, aerial drone video showed the scope of devastation in Mexico beach. Houses — what was left of them — littered the street. Closer to the ocean, squares of concrete served as the only evidence that houses had stood there just the day before.