(CNN) Deadly storms that swirled through the central US over the weekend are moving east Monday, putting close to 80 million people at risk of severe weather.

At least 15 people were killed and dozens more injured as storms tore through Texas, Missouri, Arkansas and Mississippi, spawning tornadoes and floods that left a trail of devastation.

In Arkansas, the search continued for two children separated from their mother after their car was swept away by flood waters. But the search switched to one of "recovery" rather than "rescue" of the 4-year-old and 18-month-old children, Madison County Sheriff Rick Evans told CNN affiliate TV station KHOG

The woman told deputies her car was pushed off the road and into a river in Hindsville. She was able to escape the car but couldn't save the children in the fast current after she left the vehicle.

"We're probably looking at a recovery effort, the way things happened," Evans said Sunday afternoon, as some 100 volunteers scoured the river and its banks, with help from a helicopter crew above. "I hate to look at it that way. We're hoping for the best."

The search was set to continue Monday morning.

Death toll hits 15

The death toll from the storms was raised to 15 Monday, although authorities in some areas have issued conflicting reports on the number.

A woman was killed by a falling tree near Fayetteville, Tennessee, on Sunday, Angela Phelps with the Lincoln County Department of Emergency Management confirmed to CNN.

A 2-year-old girl died in Nashville on Sunday after being struck by a heavy metal soccer goal that blew over in high winds, police said.

Flood risk

Throughout the region, tornadoes tore roofs off homes, ripped trees out of the ground and tossed cars around "like toys," one witness said. Floods swept cars off the road and downed trees and power lines that flattened homes.

12:36am CDT #SPC Day1 Outlook Enhanced Risk: this afternoon into the evening acr... https://t.co/GtEvHPMjG6 pic.twitter.com/pTf8rWLjwR — NWS SPC (@NWSSPC) May 1, 2017

And about 80 million Americans remain at risk of severe weather Monday, from Georgia through New England. "The biggest impact from these storms will be damaging winds and hail with the risk of isolated tornadoes throughout the day,"said CNN meteorologist Michael Guy.

The Storm Prediction Center said there was an enhanced risk of severe thunderstorms Monday afternoon into evening across much of the Lower Great Lakes region, the Upper Ohio Valley and the Central Appalachians into Mid-Atlantic coast.

The area includes Baltimore, Washington D.C., Pittsburgh, Buffalo and Greensboro.

The weekend's storm system also generated the risk of downstream river flooding in portions of the central United States.

Severe weather damage in Canton, Texas.

"Many areas from Louisiana up toward Missouri and into Illinois saw rainfall totals over 7 inches (with some localized amounts up to a foot) fall within 48 hours," Guy said. "Currently there are 21 million under a flood watch or warning from eastern Oklahoma up into Indiana."

The National Weather Service said flood warnings would likely be extended in parts of Oklahoma, northern Arkansas, Missouri, Illinois and Indiana, where major to record flooding would continue.

"Many of the rivers in these states have crested or (are) nearing crest and remain in moderate or major flood category. Many roads across this region are closed because of the flooding," it said.

State of emergency

Arkansas Gov. Asa Hutchinson declared a state of emergency in response to the flooding Sunday. The Arkansas Department of Emergency Management said at least five people had died in the storms.

Arkansas Gov. Asa Hutchinson declared a state of emergency.

One woman was killed when a tree fell on a mobile home in De Witt, about 80 miles east of Little Rock, ADEM spokeswoman Whitney Green said.

In Carroll County, the body of a 24-year-old woman was found in a creek.

Officials in Washington County recovered the body of a 76-year-old man in his vehicle in a field that had been submerged.

Another death in Cleburne County was included in the ADEM's death toll. The agency did not provide further details, but the Cleburne County Sheriff's Office said on its Facebook page that Fire Chief Doug Deckard died "in a tragic accident" while checking an area during a thunderstorm.

It's not clear if the latest death toll of five included the death of a 10-year-old girl in Springdale. The girl and her brother climbed a fence near a creek and the girl was swept away by rushing waters, Springdale Police said in a Facebook post. Her brother was safe and the girl's body was found around midnight, police said.

In Texas, 'heartbreaking' devastation

At least four tornadoes touched down in northeast Texas on Saturday, leaving widespread damage in Van Zandt and Henderson counties, a rural area about 60 miles east of Dallas.

One tornado was approximately a mile wide, the National Weather Service said.

The @NWS confirms one of the deadly #TexasTornadoes which took at least 4 lives was at one point 17 football fields wide! @CNNweather pic.twitter.com/5E6OFAnY9O — Pedram Javaheri (@JavaheriCNN) May 1, 2017

At least four people were killed and 49 people were hurt, Canton Mayor Lou Ann Everett said. One person is still unaccounted for. First responders from across the state went door to door Sunday to look for survivors in more than 5,000 homes in the tornado's path, she said.

"It is heartbreaking and upsetting, to say the least," the mayor said.

JUST WATCHED Churchgoers: Survived tornado by grace of God Replay More Videos ... MUST WATCH Churchgoers: Survived tornado by grace of God 01:12

Canton High School, which was used as a triage center, would be closed Monday, along with the rest of schools in Canton and Fruitvale, Everett said. A curfew is in effect in affected regions outside the city of Canton.

Texas Gov. Gregg Abbott visited Canton on Sunday to survey the damage. He commended local officials and first responders for their work and called on Texans to donate money instead of supplies.

High winds tore limbs off trees and blew them onto roads, where they blocked traffic, according to reporter J.D. Miles of CNN affiliate KTVT . Vehicles in a lot were "tossed around like toys," he said.

The twisters interrupted First Monday Trade Days, one of the largest outdoor collectibles markets in the United States. Crowds of attendees were forced to take shelter in bathrooms, CNN affiliate KLTV reported.

"We saw the the tornado drop out of the sky," said Fort Worth resident Cliff Henthorn, who was in Canton for the event. "This was crazy. It completely looks like a can opener opened this truck right in front of me. "

Fort Worth's Cliff Henthorn took this photo after Saturday's tornadoes in Canton, Texas.

The tornado hit about a mile from 17-year-old Hayley Herron's house. The next day everyone was still in shock, she said.

"The damages were horrible," she said. "Power lines and fences torn down over the roads, my friends' homes destroyed, there were buildings completely gone. Trees were split and thrown across pastures."

Officials in Mississippi blamed the weather for at least two deaths. In Rankin County, a child died from an electric shock in floodwater. Authorities did not provide information on the other death.

Two dead in Missouri

In Missouri, at least two people were killed.

A couple was left stranded in their car when flood waters began to rise in Christian County, officials said. Despite the man's efforts to rescue his wife, their car was swept away with the 72-year-old woman inside. Her body was found Saturday.

A second death was reported Sunday, but details were not available.