At least 22 people have been killed after a series of powerful tornadoes ripped through Nashville and other parts of Tennessee, flattening buildings and leaving tens of thousands of people without electricity.
The death toll provided by the Tennessee Emergency Management Agency may rise given the number of people who remain missing statewide, Governor William Lee said at a news briefing.
Rescue teams were going door to door, searching damaged structures for trapped or injured individuals, the Nashville Fire Department said.
At least 30 people were injured in Nashville, the state capital, and about 48 buildings were destroyed, with many more damaged, Fire Department Director Chief William Swann said.
US President Donald Trump said he would visit Tennessee on Friday.
"Prayers for all of those affected by the devastating tornadoes in Tennessee," he wrote in a Twitter post.
Tennessee is one 14 states that will hold primary elections on Super Tuesday.
Despite the widespread destruction, polling sites at schools and elsewhere will remain open for voting unless otherwise noted, officials said.
"We want people to exercise their rights and get out there and vote," Mr Lee said.
Lightning lit up the darkened sky as the storm rumbled through central Nashville, video posted on Twitter showed.
At daybreak on Tuesday, video footage on local television revealed levelled houses and crumbled businesses in the city of 691,000.
Nashville resident John Partipilo hid in an interior bathroom with his dog Lucille as the tornado went over his home.
"It was like this big rushing thing ... then it got real quiet," Mr Partipilo said.
"It was like a train sound, hard to explain - a growling sound."
The National Weather Service said there were eight reported tornadoes that touched down in Missouri, Tennessee and Kentucky.
