MARSHALLTOWN, Iowa (AP) — Thousands of people were without power Friday after a flurry of unexpected tornadoes swept through central Iowa, injuring at least 17 people and flattening buildings in three cities. The storms even surprised weather forecasters when they hit the region Thursday afternoon, causing extensive damage to a manufacturing plant and prompting the evacuation of a hospital.

The National Weather Service said Friday that at least five tornadoes and likely more struck. Meteorologist Jeff Johnson said it will take days to determine their strength and total number. The most extensive damage was in Marshalltown, a city of 27,000 people where 10 people were injured, brick walls collapsed into the streets, roofs were blown off buildings and the cupola of the historic courthouse tumbled to the ground.

Heavy equipment crews worked around the courthouse lawn Friday to remove entire trees blown over or shredded by the storm. The loud beep of backing trucks and grinding chain saws echoed several blocks away. Businesses and homes had gaping holes, some with roofs torn off or collapsed inward.

Alliant Energy spokesman Justin Foss said 500 utility poles needed to be replaced and 10 to 12 truckloads of poles were on their way. He said 200 crews have been called in to make repairs and restore power to 6,600 customers still without power. Natural gas service remains shut down in part of the city, he said.

In Marshalltown, the main hospital was damaged and all 40 patients at UnityPoint Health were being transferred to several other hospitals. Some buildings at the Iowa Veterans Home sustained roof damage, but no residents or staffers were injured at the facility that houses nearly 500 people, home officials said.

Such strong storms weren’t expected. Forecasting models produced Thursday morning showed only a slight chance of strong thunderstorms later in the day, said Alex Krull, a meteorologist with the National Weather Service in Des Moines, said
“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.”

Elsewhere, seven people were hurt when a tornado hit the agricultural machinery maker Vermeer Manufacturing in Pella, scattering huge sheets of metal through a parking lot and leaving one building with a gaping hole. People were still working at the plant at the time. 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.

A tornado also destroyed several homes in the Des Moines suburb of Bondurant.