Before the tornado hit Pella, it struck Bondurant in Polk County, about 15 miles northeast of Des Moines.
A statement from Vermeer Corporation in Pella says, "There has been major damage to multiple facilities".
Another tornado hit agricultural machinery maker Vermeer Manufacturing, where some people were still working, in the town of Pella, about 40 miles (64 kilometers) southeast of Des Moines. Pella Police Lt. Shane Cox told KCCI-TV there were several people from the plant transported to the hospital, but he did not provide details on the severity of those injuries.
Linda Parker, a spokeswoman for the Iowa Department of Homeland Security and Emergency Management, said seven people were treated at the scene with six taken to hospital.
A curfew was in place for 9 p.m. local time as emergency crews and volunteers scrambled to clean up the damage.
Vehicles were overturned and piled onto others.
Those who were injured were treated in hospital, none in a critical condition. All 40 of the patients at UnityPoint Health were being transferred to the health system's larger hospital in Waterloo as well as one in Grundy Center, she said.
The storm knocked out power and telephone service at city hall, officials said.
Another tornado hit the city of Marshalltown, the agency said.
"We're carefully walking through, making sure everyone is getting taken care of", Sporrer said. They could hear booms and crashes, and a gust of wind blew through the basement, but they emerged safely. Moz says, "It didn't really bother him". Houses and other structures were also damaged in Bondurant.
He said: "Houses are being torn to shreds". "It's just an absolute mess".
Additional funnels were reported east of Des Moines past Altoona, Prairie City and Colfax.
Tornadoes ripped through several Iowa towns on Thursday afternoon, destroying buildings and toppling trees. Also, an RV flipped against another home and caused damage.
Several buildings and an historic courthouse were damaged in the main business district of Marshalltown.
The CEO of Racom said all operations are up and running, even though the building looks to be damaged.