A tornado that leveled half of Parkersburg and killed seven people ranked at the top of the tornado scale, the National Weather Service said.
Sunday's twister packed winds of up to 205 mph and ranked as an EF5. The nation's last EF5 tornado flattened Greensburg, Kan., and killed 11 people on May 4, 2007.
"When you're talking about that strong a tornado, there's not a lot of structures that will save people," said Steve Teachout, a forecaster with the weather service. "Really, the only thing left of a house is the foundation."
At least some of those killed had taken shelter in their basements. An estimated 350 homes in and near Parkersburg were destroyed, and 100 others suffered major damage, Gov. Chet Culver said. About 50 people were injured.