DES MOINES, Iowa — A flurry of unexpected tornadoes swept through central Iowa, injuring at least 17 people, flattening buildings in three cities and forcing the evacuation of a hospital.

Residents — and even weather forecasters — were taken by surprise Thursday as the tornadoes hit Marshalltown, Pella and Bondurant. Ten people were injured in Marshalltown and seven at a factory near Pella, but no deaths were reported.

Alex Krull, a meteorologist with the National Weather Service in Des Moines, said forecasting models produced 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," Krull said. "If anything, we were expecting we could get some large hail, if strong storms developed."

Marshalltown, a city of 27,000 people about 50 miles northeast 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 175 feet to the ground.

The only hospital in Marshalltown was damaged, spokeswoman Amy Varcoe said. 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 emergency room in the smaller Marshalltown hospital remained open to treat patients injured in the storm, Varcoe said. Ten people hurt in the storm had been treated, she said. She did not know how serious those patients' injuries were.

Marshalltown resident Stephanie Moz said she, her husband and 2-month-old baby were in the downtown clothing store she owns when tornado sirens went off. The family sought shelter in the building's basement and heard "cracking and booms and explosions" as the tornado passed.

The storm broke out a window, ruining clothing and hats on display there, and destroyed her husband's vehicle. But she said she's relieved.

"We went through a tornado and survived," Moz said. "I'm happy."

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 tornadoes. One developed in the Marshalltown area, causing damage there, while the other started east of Des Moines and traveled through Bondurant and into Pella.

The exact number of tornadoes and their strength will be determined later.

Iowa State Rep. Mark Smith, who lives in Marshalltown, told Des Moines station KCCI-TV that the area likely will be declared a disaster area. Smith said much of downtown was damaged. He said his house and neighborhood were spared, but surrounding homes were hit.

"There are houses with windows out, houses without roofs," he said. "It's just an absolute mess."

Another tornado hit agricultural machinery maker Vermeer Manufacturing in the town of Pella, about 40 miles (64 kilometers) southeast of Des Moines. People were still working at the plant at the time. The storm scattered huge sheets of metal through a parking lot and left one building with a huge hole in it.

Seven people injured at the plant were taken to Pella Regional Health Center, hospital spokeswoman Billie Rhamy said. They all were released after being treated for their minor injuries, Rhamy said.

Gov. Kim Reynolds told WHO-TV in Des Moines that two of Vermeer's buildings in Pella were demolished in the storm. She said Vermeer was hosting 500 customers for an appreciation day when the weather hit. She credited the company's security team with moving them all to safety.

Reynolds added that in Marshalltown, the state is providing a communications trailer and workers to help maintain emergency communications there. She said Marshalltown's building housing its local communications system was damaged.