By MARGARET STAFFORD ,  Associated Press

KANSAS CITY, Mo. (AP) — Mark and Jennifer Swartz moved into their first home in November. On Tuesday, only a section of floor was left of their three-bedroom, two-bath home in Oak Grove, Missouri, after a storm system that dropped more than 30 tornadoes across the Midwest tore it apart.
"It's all we got left, just a slab," Swartz said as he surveyed the damage to his home in the town about 25 miles east of Kansas City, Missouri. "Right now, I'm in total shock. We're blown away, figuratively and literally."
Despite the destruction, Swartz said he and his wife felt blessed by God because they were eating dinner at a restaurant Monday night when the storm hit. Their home had no basement, so they would have had nowhere to hide.
"If we'd been here, we'd be dead," he said, adding, "We'll try to pick up the pieces and move on."
The Storm Prediction Center in Norman, Oklahoma, said dozens of tornadoes struck overnight in Missouri, Kansas, Iowa and Illinois. The National Weather Service was assessing the exact number and strength of twisters Tuesday. The same storm system brought huge hailstones and powerful winds as far south as the Ozark Mountains in Arkansas and as far north as Wisconsin.
The Swartz's home was one of 483 homes and 10 to 12 commercial buildings with some type of damage in Oak Grove, said Sni Valley Fire Protection District Chief Carl Scarborough. Twelve people were treated for non-life-threatening injuries, he said.
"It looks like the injuries are minimal so, based on some of the damage I've seen, it's rather amazing" that no one died, Oak Grove Mayor Jeremy Martin said in a Tuesday morning news conference.
Missouri Gov. Eric Greitens declared a state of emergency and surveyed the damage in Oak Grove on Tuesday.
In Smithville, Missouri, between 60 and 70 homes were damaged or destroyed, Police Chief Jason Lockridge said. The damage will be "well north of seven figures" in the town of around 9,000 residents about 25 miles north of Kansas City. No serious injuries were reported.
Across the state line, one hangar was destroyed, at least five others were damaged and airplanes were flipped onto their sides at the Johnson County Executive Airport, in Olathe, Kansas, according to Trent Pittman, the county's assistant director of community preparedness.
Pittman said dozen of homes were damaged in the nearby suburb of Leawood, where trees and power lines are down. No injuries were reported in either location.
Oak Grove opened its Civic Center Monday evening for residents displaced by the twister but no one stayed overnight, said Sherri Odell, a spokeswoman for The American Red Cross of Western Missouri.
Police said several homes, barns and sheds were damaged in rural areas near Plattsburg and Lathrop in Missouri, and four people were treated for minor injuries.
The system weakened as it moved east across Missouri but dropped an EF-1 tornado in the St. Louis suburb of Wentzville, injuring two people and damaging homes and businesses, the weather service said in a preliminary report.
In Iowa, where hurricane-force winds were reported, the Muscatine Fire Department said several homes and businesses were damaged Monday night as power lines were knocked down. The weather service said tornadoes were reported in Clinton County, and a service employee reported sighting a twister southwest of the Davenport Municipal Airport in Scott County. A suspected tornado damaged a school in the south-central Iowa community of Seymour.
A likely tornado also touched down northwest of the Twin Cities in Minnesota, damaging buildings, trees and power lines.
The storm system was weakening as it moved to the east but the Storm Prediction Center said parts of Louisiana, Mississippi and Alabama could see severe thunderstorms Tuesday.