KANSAS CITY, Mo. >> Mark and Jennifer Swartz moved into their first home in November. Today, only a section of floor was left of their three-bedroom, two-bath house 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 house 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 injuries that weren’t life-threatening, 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.

The National Weather Service said Tuesday that the Oak Grove tornado was an EF3, with an estimated peak wind of 152 mph.

In Smithville, Missouri, an EF2 tornado with peak winds of 132 mph, damaged or destroyed between 60 and 70 homes, 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.

A suburban Kansas City airport was hit by straight-line winds averaging 80 to 85 mph, not a tornado, the weather service said. The Johnson County Executive Airport in Olathe, Kansas, reopened to limited air traffic but remained closed to the public Tuesday. Nine public and three private hangars were damaged, with one demolished, and officials were still working to determine how many airplanes were damaged.

About 46 homes sustained some damage, with a handful having major damage, in the nearby suburb of Leawood, Kansas, said Johnson County spokeswoman Sharon Watson. No injuries were reported in Olathe or Leawood.

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.

EF1 tornadoes, which have wind speeds of 86 mph to 110 mph, were reported in three Missouri communities: the Kansas City suburb of Lee’s Summit, Macks Creek in southwest Missouri and Wentzville near St. Louis.

In northeast Missouri, Shelby County canceled classes after strong winds damaged several school buildings. And in Odessa, about 40 miles east of Kansas City, people were told to boil their water because the city’s water treatment plant was damaged.

In Iowa, where hurricane-force winds were reported, the National Weather Service in Davenport confirmed three injuries and 80 homes damaged in Muscatine from a tornado that traveled nearly 2 miles leaving a swath of damage 200 yards wide. The EF2 tornado struck Monday night with peak winds of 115 miles per hour.

Another EF2 tornado swept along 25 miles through Blue Grass, northwest Davenport and Eldridge damaging a home, farm buildings, trees and power poles. A suspected tornado also damaged a school in the south-central Iowa community of Seymour.

Minnesota got hit with two tornadoes Monday evening — the earliest twisters to ever strike the state. Forecasters say one damaged buildings and took down trees and power lines near Zimmerman, about 35 miles north of Minneapolis-St. Paul. The second caused damage in Clarks Grove, about 15 miles north of Albert Lea in southern Minnesota.

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 today.