At least nine people have died after two deadly tornadoes struck central Tennessee, including one that ripped across Nashville and caused about 40 buildings to collapse around the US city.
Authorities are continuing to search the wreckage for injured people.
Police pleaded with people to stay indoors, at least until daybreak could reveal the dangers of a landscape littered with rubble from walls and roofs, as well as snapped power lines and downed trees.
Schools, courts and transport lines were closed, and four polling stations were moved only hours before Super Tuesday voting was set to begin.
Nashville mayor John Cooper told the Tennessean while visiting an emergency shelter: “A tornado skipped across the county.
“You do have people at the hospital and frankly there have been fatalities.”
The tornado reportedly stayed on the ground into Hermitage, about 10 miles east of the city.
Other areas reporting extensive damage included Mt Juliet and Germantown.
Local police in Mt Juliet tweeted: “Our community has been impacted significantly. We continue to search for injured. Stay home if you can.”
Police officers and fire crews were responding to about 40 building collapses around the city, Metro Nashville police said.
John C Tune Airport, Nashville International’s sister airport in West Nashville, “sustained significant damage due to severe weather”, spokeswoman Kim Gerlock said.
Several hangars have been destroyed and power lines are down, she said, adding that there are no reported injuries.
Ms Gerlock asked that the public avoid the airport until further notice and that the Airport Authority has activated its Emergency Operations Centre to coordinate response.
A video posted online from east Nashville showed what appeared to be a well-defined tornado moving quickly across the city. Lightning repeatedly flashed while much of the city was in the dark.
Images on social media showed extensive damage to buildings, mangled wires on downed power lines and structures that are now unrecognisable as the tornado had reduced them to rubble.
One photo showed a white vinyl fence that had fallen on a car. Another showed the roof and walls gone from a building that still had what appeared to be boxes stacked on shelves.
A reported gas leak forced an evacuation of the IMT building in the Germantown community, according to WSMV-TV. Photos showed dozens of people in the street carrying their belongings not long after the tornado moved through the city.
The American Red Cross of Tennessee said on its Twitter account that a shelter had been opened for displaced residents at the Nashville Farmers Market, just north of the state capitol.