In Pella in the state's south-east, a company that manufactures industrial and agricultural equipment reported "major damage" after one tornado hit.
Video showed the tornado taking off the iconic cupola of the Marshall County Courthouse, a limestone building on the National Register of Historic Places. Staff are moving patients to UnityPoint Health - Waterloo and UnityPoint Health - Grundy Center. A spokesperson was unsure of the severity of the damage.
Pella Police Lt. Shane Cox told KCCI-TV some people from Vermeer Manufacturing were taken to a hospital, but he didn't know the extent of injuries or the number of people.
'If anything, we were expecting we could get some large hail, if strong storms developed'.
Bondurant, Marshalltown and Pella are among the communities struck by a strong line of supercell storms generating twisters.
National Weather Service meteorologist Rod Donavon said two primary storms spawned the series of damaging tornadoes.
Tornadoes sweep through US state of Iowa
Newendorp said says the plant activated its storm warning system and workers were in shelters when the storm hit, scattering huge sheets of metal through a parking lot and leaving one building with a huge hole in it. Vehicles were overturned and piled onto others.
According to CNN affiliate WOI, another tornado damaged houses in Bondurant, about 15km from Des Moines.
Additional funnels were reported east of Des Moines past Altoona, Prairie City and Colfax and funnel clouds were reported further north near Iowa Falls. "It's just an absolute mess". Officials said everyone should stay off the streets unless they have an emergency. The Vermeer Corporation said on Facebook that the severe weather hit multiple facilities at 4 p.m.
Seven people were transported to Pella Regional Health Center with minor injuries - all have been treated and released, he said.
A woman working at Hammer Medical Supply in the city's downtown said her building suffered damage, as did nearby buildings including The Orpheum, a theater built in 1948.