At least 24 people are now known to have died after nearly a week of tornadoes, heavy rains and flooding in several US south-central states.
Six people died in Texas after a new tornado touched down near Dallas late on Saturday.
Earlier, the bodies of a man and a woman – who were missing after a tornado in Mississippi – were found, bringing the state’s death toll to 10.
The storms across the South have been unusually powerful for winter.
Six people died in Tennessee. Arkansas and Alabama each reported one fatality.
Meanwhile, officials said Texas and Oklahoma could be hit with a “historic blizzard”, bringing up to 16in (41cm) of snow.
Motorists were warned they could face icy roads.
In Texas, four people died in traffic accidents Garland, just east of Dallas, on Saturday evening.
Garland police spokesman Joe Harn said this happened during a large storm, the Associated Press news agency reports.
Another two people were reported dead at a petrol station in the nearby town of Copeville.
The National Weather Service confirmed that tornados had touched down near Dallas and several other towns.
In Mississippi, 56 injuries have been reported and more than 400 houses have been destroyed or damaged.
At least 20 tornadoes hit the state, knocking down trees and leaving thousands without power over Christmas holidays.
One large tornado reportedly touched land in Mississippi and tore a path more than 100 miles (160 km) long to Tennessee.
While extreme weather in the US before Christmas is not unknown, meteorologists say that unseasonably high temperatures in some areas contributed to the severity of the storms.
One year ago a tornado hit south-eastern Mississippi, killing five people and injuring dozens more.
A storm on Christmas Day in 2012 which included several tornadoes damaged homes from Texas to Alabama.