Three tornadoes were confirmed by the US National Weather Service in Canton, a city about 60 miles (95 km) east of Dallas in Van Zandt County.
The winds flipped over cars, snapped trees, destroyed houses and left roads strewn with debris and fallen power lines, according to photographs and video published by the Dallas Morning News.
"We have at least four fatalities," Canton Mayor Lou Ann Everett said at a news conference on Sunday, adding that number could rise. "The damage was extensive in the affected area. It is heartbreaking and upsetting." Forty-nine people had been treated for injuries, she said.
Earlier a Canton fire department captain said he believed five people had been killed.
The mayor urged people to stay away from a sprawling flea market known as First Monday Trade Days, as crews tried to clean up debris.
Texas Governor Greg Abbott sent a search and rescue team to the area.
The storms caused floods in neighboring states, killing a 72-year-old woman in southwestern Missouri who was washed away in her car, according to local media reports.
At least two other people reportedly died in storm-related incidents, while two children were missing after their mother's car was swept from a road by floodwaters in Madison County. As many as 100,000 homes and businesses lost power, and Gov. Asa Hutchinson declared a state of emergency on Sunday night.
In Mississippi, a person was killed after a tree fell on their house in Durant, ABC reported. The governors of Missouri and Oklahoma declared states of emergency.
In the St. Louis area, severe thunderstorms were forecast through Sunday. Some people were told to evacuate and 33 rescues were conducted, mostly in the state's central and southwestern regions, Missouri Gov. Eric Greitens said.
(Editing by Chris Michaud)
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
Follow NDTV for latest election news and live coverage of assembly elections 2019 in Maharashtra and Haryana.
Subscribe to our YouTube channel, like us on Facebook or follow us on Twitter and Instagram for latest news and live news updates.