At least 12 people are dead after 15 tornadoes blew through the Midwest overnight, according to authorities, and the death toll is expected to rise.
The extensive damage caused by the storms in at least five states is only beginning to become clear. Meanwhile, more tornado watches are in effect in Kentucky and Tennessee, according to the National Weather Service.
The tornadoes touched down across Nebraska, Kansas, Missouri, Kentucky and Indiana Tuesday night, the National Weather Service Storm Prediction Center said.
At least six people -- four women and two men -- were killed in the town of Harrisburg, Ill., according to Lt. Tracy Felty of the Saline County Sheriff's Office. The tornado hit Harrisburg, 50 miles southwest of Evansville, Ind., around 5 a.m., leveling a wide swath of homes and other buildings.
The National Weather Service said the twister was about 200 yards wide and ranked as an EF4 -- the second-highest rating given to twisters -- with peak winds of 170 mph.
During a news conference this afternoon, Harrisburg Mayor Eric Gregg said that the city was in "search and recovery mode."
"We have devastation in our community like we've never seen," he said. "We are doing everything we can to protect this community. ... That is our mission. That is our task now."
Sheriffs' officials earlier estimated the number of people killed in the 9,000-resident town to be as high as 10, but later said that number was incorrect. An estimated 100 people were injured in the storm, officials said.
Vince Ashley, CEO of the town's medical center, told The Associated Press that some of the victims were pronounced dead on arrival at the 78-bed hospital, which also sustained damage.
"It's been quite a rush. They're still coming in, but we've been able to keep up with the flow of injured coming in," Ashley told The Associated Press. "Helicopters have been coming in and out here all morning."
The physical damage in Harrisburg was said to be extensive, with power lines down and as many as 300 homes and 25 businesses damaged or destroyed, according to officials at the sheriff's office.
Schools in Harrisburg were canceled and officials asked non-residents to stay away, according to local affiliate WSIL.
Another confirmed death came in Missouri, where the entertainment destination of Branson, Mo., was hit hard by the storms.
A tornado blew through a mobile home park outside of Buffalo, Mo., killing one person and injuring 13 others, according to officials with the Dallas County Sheriff's Office. Two more deaths were reported in the areas of Cassville and Puxico, The Associated Press reported.
The final casualty count in Branson remained unclear as sheriff officers moved from house to house to search for victims.
At least a dozen injuries have already been confirmed and the storms caused heavy damage to the city's famous theaters, National Weather Service meteorologist Mike Griffin told The Associated Press.
Local affiliate KMBC reported windows were blown out of the Hilton Convention Center in Branson and 32 people were treated for injuries in at least one local hospital.
Missouri Gov. Jay Nixon issued a state of emergency order Wednesday morning and shelters for displaced residents were opened throughout the state.
In Tennessee, three people died as the storms destroyed homes in Cumberland and Dekalb Counties, the AP reported.
In Kansas, the small town of Harveyville, just south of Topeka, was hit especially hard by a tornado that touched down just after 9 p.m. local time Tuesday.
"The town was taken out by about 40 percent of the buildings in the community," Sharon Watson, director of public affairs for the Kansas Adjutant General's Office told ABC News. "A significant amount of it has been destroyed. A lot of homes damaged, a lot of buildings down including a church and an apartment complex."
Officials added that one person trapped in a building had to be extricated from underneath debris and was taken to the hospital in critical condition.
One man in Harveyville described the storm to ABC News as, "just like a shotgun went off."
Kansas Gov. Sam Brownback also declared a state of emergency after the storm hit and caused highway closings and downed power lines throughout the area.
The National Weather Service reported lesser-force tornadoes occurred elsewhere in the state, touching down southwest of the town of Hutchinson.
The Associated Press contributed to this report.