LAKE CITY, Ark. (AP) — Tornadoes and violent winds flattened homes and ripped apart buildings from Oklahoma to Indiana in the first round of storms that are expected to bring record-setting rains and life-threatening flash floods across the nation’s midsection in the coming days.

At least six people were killed in western Tennessee, Missouri and Indiana in the first wave on Wednesday and early Thursday that spun off powerful tornadoes — one launching debris nearly 5 miles (8 kilometers) above the ground in Arkansas.

Homes along the highway that crosses through Lake City, Arkansas, had completely collapsed, their brick walls crushed and roofs gone. Three cars were tossed into trees. Workers were using bulldozers to clear debris.

“I don’t really know how to explain it,” said Cody Ferguson, who hid in a storm shelter with neighbors while the twister roared above them. “Just real loud rumbling, a lot of bangs, debris.”

The home he had built from the ground up was destroyed, and he said a neighbor from across the street was seriously injured.

Among the deaths, at least four people were killed in western Tennessee, including a man and his teenage daughter whose home was destroyed, and an Indiana man who died after his pickup truck struck downed powerlines.

More than 90 million people were at risk of severe weather across an area stretching from Texas to Minnesota and Maine, according to the Oklahoma-based Storm Prediction Center.

Potentially deadly flash flooding was forecast through Saturday for the South and Midwest as severe thunderstorms blowing eastward become supercharged. The potent storm system will bring “significant, life-threatening flash flooding” each day, the National Weather Service said.

With more than a foot (30 centimeters) of rain possible over the next four days, the prolonged deluge “is an event that happens once in a generation to once in a lifetime,” the weather service said. “Historic rainfall totals and impacts are possible.”

Water rescue teams were being staged across the region and the Federal Emergency Management Agency was ready to distribute food, water, cots, generators and meals.

Forecasters attributed the violent weather to warm temperatures, an unstable atmosphere, strong wind shear and abundant moisture streaming from the Gulf.

Tornadoes touch down, and more could be coming

Under darkened skies Thursday morning, the remains of a used car dealership in Selmer, Tennessee, stood gutted by the storm with the roof ripped off. Shards of debris scattered across the car lot and wrapped around the mangled trees.

The Tennessee Highway Patrol released video of lightning illuminating the sky as troopers, Selmer police, sheriff’s deputies and firefighters scoured the rubble of a decimated home early Thursday morning, looking for anyone trapped.

In neighboring Arkansas, a tornado emergency, the weather service’s highest alert, was briefly declared around Blytheville on Wednesday evening, with debris lofted at least 25,000 feet (7.6 kilometers), according to weather service meteorologist Chelly Amin.

The Arkansas Division of Emergency Management reported damage in 22 counties due to tornadoes, wind gusts, hail and flash flooding.

In far western Kentucky, four people were injured while taking shelter in a vehicle under a church carport, said the emergency management office in Ballard County. Multiple buildings and homes were badly damaged from what appeared to have been a tornado, the agency said.

Warehouse collapse is part of damage in Indiana

Emergency crews worked for several hours to free a warehouse worker trapped after a roof and a wall collapsed near Indianapolis. The woman was conscious and talking during the rescue on Wednesday.

“It was just heavy debris that had fallen on top of her,” Brownsburg Fire Department spokesperson Kamrick Holding told WTHR-TV. “She happened to be in the wrong place at the wrong time.”

Wind gusts blew over semitrucks, downed power lines and caused power outages that disrupted classes in at least 10 school districts in Indiana.

More than half a million customers in Indiana, Ohio, Kentucky, Arkansas, Tennessee, West Virginia, Mississippi, Missouri and Texas were without power early Thursday following the peak of the storms, according to PowerOutage.us.

Flash flood threat looms over many states

Round after round of heavy rains are expected from Texas to Kentucky through Saturday. Forecasters warned that the lingering storms could track over the same areas repeatedly, producing dangerous flash floods capable of sweeping cars away.

Parts of Arkansas, Missouri, Kentucky, Illinois and Indiana could see rains totaling up to 15 inches (38 centimeters), the weather service warned.

Western Kentucky residents were bracing for historic amounts of rain and flooding in places that normally don’t get overwhelmed by water, Gov. Andy Beshear said.

Flash flooding is a particular worry in rural areas of the state where floodwaters can quickly rush off the mountains into the hollows. Less than four years ago, dozens died in flooding across eastern Kentucky.