An unexpected flurry of tornadoes has swept through central Iowa, injuring at least 17 people, flattening buildings in three cities and forcing the evacuation of a hospital.
The tornadoes hit Marshalltown, Pella and Bondurant as surprised residents ran for cover.
The storms injured 10 people in Marshalltown and seven at a factory near Pella, but no deaths were reported.
Marshalltown, a city of 27,000 people about 50 miles north east of Des Moines, appeared to have been hit the hardest. Brick walls collapsed in the streets, roofs were blown off buildings and the cupola of the historic courthouse tumbled 175ft to the ground.
The only hospital in Marshalltown was damaged, spokeswoman Amy Varcoe said. All 40 patients at UnityPoint Health were being transferred, she said.
The emergency room in Marshalltown remained open to treat patients injured in the storm, Ms Varcoe said. Ten people hurt in the storm had been treated, but she did not know how serious their injuries were.
Weather forecasters said the tornadoes formed suddenly and took them by surprise.
Alex Krull, a meteorologist with the National Weather Service in Des Moines, said forecasting models produced on Thursday morning showed only a slight chance of strong thunderstorms later in the day.
“This morning, it didn’t look like tornadic supercells were possible. If anything, we were expecting we could get some large hail, if strong storms developed.”
Additional funnels were reported as the storm moved east of Des Moines past Altoona, Prairie City and Colfax.
National Weather Service meteorologist Rod Donavon said two primary storms spawned the series of damaging tornadoes. One developed in the Marshalltown area, while the other started east of Des Moines and travelled through Bondurant and into Pella.
Iowa State representative Mark Smith, who lives in Marshalltown, told Des Moines station KCCI-TV that the area will probably be declared a disaster area.
Mr Smith said much of the central area was damaged. He said his house and neighbourhood were spared, but surrounding homes were hit.
Another tornado hit agricultural machinery maker Vermeer Manufacturing in the town of Pella, about 40 miles south east of Des Moines. People were still working at the plant at the time.
The storm scattered huge sheets of metal through a car park and left one building with a huge hole in it.
Seven people injured at the plant were taken to Pella Regional Health Centre, hospital spokeswoman Billie Rhamy said. They all were released after being treated for minor injuries.