Kevin Johnson last saw his son Scott wading through the rushing water with his 74-year-old grandmother on his back.

Scott Johnson had already saved his father, his uncle and sister as a flash flood ravaged the rural town of Flat Gap. He returned to their cluster of trailers for his grandmother and teenage nephew and started to carry them to higher ground. As the flood raged out of control, he wedged his nephew safely into a high tree before the water washed Johnson and the grandmother away.

The grandmother, Willa Mae Pennington, was found dead on Tuesday among debris from the family’s shattered mobile homes, the Johnson County coroner, JR Frisby, confirmed. Scott Johnson, 34, is one of six people still unaccounted for after the raging Monday afternoon flood.

Rescue crews combing the hilly Appalachian terrain on Tuesday were hampered by more heavy rains, swarming mosquitoes, soupy humidity and knee-deep mud.

“It just wears your legs out to walk,” said Gary McClure, the local emergency management director. “You walk from here to there in that mud and you’re ready to sit down. It just pulls you down.”

Authorities called off the search around 8pm on Tuesday. After daybreak on Wednesday, a convoy of national guard vehicles and heavy equipment, including excavators and dump trucks, travelled down the road toward the hardest-hit area as crews prepared to resume the search.

Facebook Twitter Pinterest Melissa Greene salvages muddy clothes from her trailer in the Pennington Trailer Park in Flat Gap. Photograph: Charles Bertram/AP

“They will be going back over the same areas again and starting new searches that we haven’t gone over so far. Every inch of all this debris has not been searched through yet,” Frisby said on Wednesday. “Just haven’t had time.”

On Tuesday, emergency personnel went door-to-door in the hardest-hit neighbourhoods, searching for those who might be trapped in their homes, Trooper Steven Mounts of Kentucky state police said. Like Scott Johnson’s nephew, some were rescued from trees, Price said.

Kentucky’s governor, Steve Beshear, declared a state of emergency to give local officials immediate access to state resources to assist in recovery efforts.

The search area stretches more than eight miles, from the town of Flat Gap south to Staffordsville – an area with 500 homes and 1,200 residents about 120 miles east of Lexington, police told a news conference. Authorities estimate more than 150 homes were destroyed.

Hebert Hayden, 78, left home with his wife for a doctor’s appointment. While they were away, their mobile home was swept from its foundation and crashed nearby. They lost everything.

“All I can say is God was on our side,” he said. “If we would have been here, we would have drowned.”

The roads now are lined with empty foundations, where trailers or homes once stood. Cars are flipped upside down and trees uprooted. Fifteen people were treated at a local hospital and released.

Frisby identified the second known casualty as Herman Eddie May Sr, 65. May was driving alone in a sport-utility vehicle when floodwaters from the Patterson creek started to sweep him away. He drowned after he got out and was swallowed by the rising water, Frisby said.

Facebook Twitter Pinterest A house was moved from its foundation by the flooding in Flat Gap. Photograph: Charles Bertram/AP

Doris Hardin watched the water rise from the window of her mobile home. Her lights flickered off then her neighbour banged on the door, shouting for her to flee. She and her neighbours had seconds to react. Hardin sprinted up a hill, as utility poles crashed down around her.

The water swept up Hardin’s trailer, her two cats still inside, and jammed it into a growing heap of mangled debris: other mobile homes, wrecked cars, snapped trees and downed power lines.

Hardin, now staying with her father, had still not found her cats on Tuesday afternoon, and feared she never would. “I don’t think anything else is going to be salvageable,” she said.

Authorities worried that the muddy, rushing creek, still swollen on Tuesday afternoon, had not finished its destruction.

A strong thunderstorm passed through the area on Tuesday evening, dumping heavy rain and lashing the area with high winds.

Buddy Rogers, spokesman for Kentucky emergency management, said the ground is thoroughly saturated from the overnight rains and heavy storms of the past several weeks. More water will have nowhere to go but into roads, yards and homes, he suspects. Many of the same areas are likely to be underwater again. The waterlogged ground also threatens to topple more power lines, trees and utility poles in high winds.

Facebook Twitter Pinterest Johnson County and state officials give an update about the deadly flooding. Photograph: Charles Bertram/AP

“Any more rain at all is going to be detrimental. It will hurt us,” said Bobby Moore, a Johnson County 911 dispatcher. Moore said the flood washed away a number of rural roads and left others clogged with fallen trees and debris, forcing rescuers to turn to all-terrain vehicles to reach homes and search for residents.

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A helicopter hovered overhead to aid in the search, which included more than 100 rescuers from local departments, the state police, the department of fish and wildlife and the national guard.

Authorities were trying to keep as many people off the roads and out of the area as possible. Rogers recommended that people who live in flood-prone areas find an alternative place to stay until the storms pass.

Homes there have no power or phone service, and many have been severely damaged by floodwaters. A shelter was opened at the Paintsville recreation center, though only a handful of people were there on Tuesday afternoon. Most displaced residents were staying at hotels or with family, Moore said.