The death toll from Hurricane Michael rose to 17 across four states on Friday, law enforcement officials said, as rescue crews hampered by communications failures searched the hardest-hit communities in the Florida Panhandle.

The number of fatalities was expected to rise further as rescuers go door to door and comb through the rubble in oceanfront communities such as Mexico Beach, Port St. Joe and Panama City that bore the brunt of the storm's wrath.

Michael struck Florida's northwest coast near the small town of Mexico Beach on Wednesday afternoon with top sustained winds of 155 miles per hour (250 km/h), pushing a wall of seawater inland and causing widespread flooding.

The storm tore entire neighborhoods apart, reducing homes and businesses to piles of wood and siding, damaging roads and leaving scenes of devastation that resembled the aftermath of a carpet-bombing operation.

US Army personnel used heavy equipment to push a path through debris in Mexico Beach to allow rescuers through to search for trapped residents, survivors or casualties, as Black Hawk helicopters circled overhead. Rescuers from the Federal Emergency Management Agency (FEMA) used dogs, drones and GPS in the search.

"We prepare for the worst and hope for the best. This is obviously the worst," said Stephanie Palmer, a FEMA firefighter and rescuer from Coral Springs, Florida.

Much of downtown Port St. Joe, 12 miles (19 km) east of Mexico Beach, was flooded after Michael snapped boats in two and hurled a large ship onto the shore, residents said.

"We had houses that were on one side of the street and now they're on the other," said Mayor Bo Patterson, who watched trees fly by his window as he rode out the storm in his home seven blocks from the beach.

Patterson estimated 1,000 homes were completely or partially destroyed in his town of 3,500 people.

Jordon Tood, 31, a charter boat captain in Port St. Joe, said: "There were mandatory evacuation orders, but only idiots like us stuck around."

"This was my sixth (hurricane), so I thought I was prepared," he said. 

In Apalachicola, about 30 miles (48 km) east of where the storm made landfall, a little less than half of the 2,200 people stayed and rode out the storm, residents said. 

Checking door to door

The storm peeled back part of the gym roof and tore off a wall at Jinks Middle School in Panama City. A year ago, the school welcomed students and families displaced by Hurricane Maria in Puerto Rico.

"I have had employees going to the communities where our kids live, going door to door and checking," Principal Britt Smith said by phone. "I have been up since 3:30 or 4 a.m. emailing and checking on staff to see if they are safe. So far, everybody seems to be very safe."

With a low barometric pressure recorded at 919 millibars, a measure of a hurricane's force, Michael was the third strongest storm on record to hit the continental United States, behind only Hurricane Camille on the Mississippi Gulf Coast in 1969 and the Labor Day hurricane of 1935 in the Florida Keys. 

It weakened overnight to a tropical storm.

Fast-moving Michael, a Category 4 storm on the five-step Saffir-Simpson hurricane scale when it came ashore, was about 15 miles (25 km) northeast of Norfolk, Virginia, at 10 p.m. (0200 GMT), with top sustained winds of 50 mph (80 km/h) as it headed for the Atlantic coast, the US National Hurricane Center said. 

It was toppling trees and bringing life-threatening flash flooding to areas of Georgia and Virginia, which are still recovering from Hurricane Florence, as it marched northeast.

At least seven people were killed by falling trees and other hurricane-related incidents in Florida, Georgia and North Carolina, according to state officials.

Emergency services carried out dozens of rescues of people caught in swiftly moving floodwaters in North Carolina.

Many of the injured in Florida were taken to hard-hit Panama City, 20 miles (32 km) northwest of Mexico Beach.

Gulf Coast Regional Medical Center treated some but the hospital evacuated 130 patients as it faced challenges running on generators after the storm knocked out power, ripped off part of its roof and smashed windows, according to a spokesman for the hospital's owner, HCA Healthcare Inc. 

Almost 1.2 million homes and businesses were without power from Florida to Virginia on Thursday because of the storm. The number of people in emergency shelters was expected to swell to 20,000 across five states by Friday, said Brad Kieserman of the American Red Cross. 

Brad Rippey, a meteorologist for the US Agriculture Department, said Michael severely damaged cotton, timber, pecan and peanut crops, causing estimated liabilities as high as 1.9 billion US dollars and affecting up to 1.5 million crop hectares.

Michael also disrupted energy operations in the US Gulf of Mexico as it approached land, cutting crude oil production by more than 40 percent and natural gas output by nearly a third as offshore platforms were evacuated.