The National Weather Service said a preliminary examination of photos and videos from around Winterset, Iowa, suggested damage from a tornado with wind speeds between 136 and 165 miles per hour.
Six people were killed, including two children, in Iowa on Saturday after what the authorities said appeared to be tornadoes battered communities across the state.
Four adults were injured, including three who were in serious condition and one who had life-threatening injuries, said Diogenes Ayala, the director of the Madison County Emergency Management Agency.
“The best thing the community can do is just to not go to these areas,” Mr. Ayala said at a news conference late on Saturday. “Let people that are living there — let them clean up. Give them some space. This is pretty devastating for our community.”
Mr. Ayala said that people should call the authorities if they know someone who is missing.
The deaths — including two children younger than 5 — occurred at different locations. Mr. Ayala did not disclose more details about the deaths because all of the families of the victims had yet to be notified.
Mr. Ayala estimated that 25 to 30 homes had been destroyed but said a fuller assessment would come in the morning.
The National Weather Service said that a preliminary examination of photos and videos from around Winterset, a city in Madison County, suggested damage from a tornado with wind speeds between 136 and 165 miles per hour.
The agency’s survey teams will further investigate the damage on Sunday, officials said.
Video posted on social media and recorded south of Winterset shows the aftermath of the severe weather: piles of debris, smoke and a car flipped upside down.
Several homes in Norwalk, about 10 miles south of Des Moines, were damaged along with the city’s public works site and some local businesses, said Shelby Hisel, a city spokeswoman.
As of late Saturday, no injuries had been reported in Norwalk. Ms. Hisel was not sure whether the damage was the result of a tornado or another extreme weather event, such as high winds, and said the city would assess the damage in the morning.
The Des Moines International Airport was evacuated for more than 20 minutes as a precaution in response to a tornado warning, causing flight delays, said Kayla Kovarna, an airport spokeswoman.
