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At least 11 people were killed and dozens more were injured after severe storms that included powerful tornadoes hit the South, including Arkansas, Missouri and a region of Texas east of Dallas, officials said.

At least four tornadoes touched down in east Texas on Saturday afternoon and evening, the National Weather Service said.

Canton, Texas, Mayor Lou Ann Everett said Sunday that at least four people were killed and 49 others were injured but that the situation was "very fluid" and could change.

"The damage was extensive. It is heartbreaking," she said.

Texas Gov. Greg Abbott said the damage was "devastating" during a news conference with local officials Sunday afternoon.

"You saw homes and other buildings that were incompletely flattened, as well as others that were nothing more than rubble," he said, adding that he saw "large swath after large swath of devastation."

In lieu of clothes, Abbot said people should donate money to help those affected by the storm — or even a warehouse for first responders to hold supplies.

Everett had told NBC News in a phone interview Saturday night that five people were believed to have been killed. Power was also knocked out and the full scope of the damage was not yet known, she said.

"We won't know what exactly we are dealing with until the sun comes up," Everett said. "We have no power. We have three major transmission stations that are damaged."

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East Texas Medical Center previously reported that 52 people were being treated at three hospitals because of the severe weather and that one of those patients was in critical condition.

Video taken from the scene showed tornadoes touching down and thunder. Dozens of cars were overturned on Interstate 20, east of Canton, NBC Dallas-Fort Worth reported. The tornadoes hit in Henderson and Van Zandt counties, according to the weather service.

Desirae Rasmussen of Canton survived the tornado, but her home was seriously damaged. "Every last one of us walked away. But we have nothing left down there," Rasmussen told NBCDFW.

"We were all sitting in the hallway and the roof collapsed on us. By the time it was all over, we went outside. We had a three-level house, and we're down to the last level, and half of that roof is gone," she said.

The tornadoes in Texas occurred as storms swept across the parts of the South and Midwest on Saturday, with flash flood warnings in place for a swath stretching from eastern Oklahoma to western Kentucky and parts of Illinois.

In Missouri on Saturday, a woman drowned after the car she was in was swept away by floodwaters in Clever, a town about 20 miles southwest of Springfield, the Missouri State Highway Patrol said. The husband of Madelaine Krueger, 72, tried to rescue her before the vehicle was swept away but was unsuccessful, the highway patrol said.

A 2-year-old girl was killed Sunday in Antioch, Tennessee, when a heavy metal soccer goal toppled onto her in high winds, Nashville police said.

In Mississippi, two storm-related deaths were reported Sunday, in Holmes County and Rankin County, where a child died from electric shock in floodwaters, the Mississippi Emergency Management Agency said. No details of the Holmes County death were immediately available.

"We're having major flooding like I've never seen since I've been here in town," Neosho, Missouri, Mayor Ben Baker said. Vehicles in the town of 12,000 south of Joplin were pushed by floodwaters into trees and homes after creeks spilled over their banks.

In Arkansas, a person was killed after a tree fell onto a mobile home in Dewitt, Arkansas County Emergency Management spokeswoman Whitney Green said.

And a 10-year-old girl was killed after being swept away by rushing waters in Springdale, Arkansas, on Saturday, police said on Sunday.

The Cleburne County Sheriff's Office said in a statement Sunday afternoon that Cove Creek Pearson Fire Chief Doug Deckard died during a "tragic accident" while serving in the middle of a torrential thunderstorm.

On the other side of the state in Fayetteville, authorities said they conducted 20 water rescues Saturday after flooding there.

And in Madison County, Arkansas, authorities were looking for two children — a 4-year-old boy and an 18-month-old girl — who were missing after being separated from their mother as her car got stuck in high water on Saturday night. Authorities said on Sunday that the search for the missing toddlers had become a recovery operation.

Oklahoma declared a state of emergency on Saturday. Oklahoma Gov. Mary Fallin's office said there was widespread flooding in Cherokee County, where there were 14 water rescues Saturday, and flooding in Adair County. Baseball-size hail fell west of the town of Cameron, damaging power lines.

More than 12,000 customers in central Oklahoma were without electricity as of Saturday evening, utility OGE Energy Corp. said.

Missouri Gov. Eric Greitens declared a state of emergency for his state on Friday, NBC affiliate KSDK of St. Louis reported. Abbott said a task force was being sent to help Texas communities affected by the tornadoes and severe weather.