Dozens of tornados have swept the US Midwest leaving at least six people dead and flattening entire neighbourhoods.
An elderly man and his sister were killed when a tornado hit their home in rural southern Illinois. Four other people were killed in the state, the hardest hit.
State governor Pat Quinn declared seven counties disaster areas.
With communications difficult and many roads impassable, it remained unclear what the final death and destruction figures are.
Between 250 and 500 homes were either damaged or destroyed in the town of Washington when the storms hit on Sunday. Mayor Gary Manier said: "Everybody's without power, but some people are without everything. How people survived is beyond me."
The tornado cut a path from one side of town of 16,000 people to the other, knocking down power lines uprooting trees and rupturing gas pipes.
One local said he walked through the area immediately after the tornado struck and "couldn't even tell what street I was on."
"Just completely flattened - some of the neighbourhoods here in town, hundreds of homes."
Just how many tornados hit was unclear. According to the National Weather Service's website, a total of 65 tornados struck, most of them in Illinois. But meteorologists said the total might fall because emergency workers, tornado spotters and others often report the same tornado.
Such strong storms are rare this late in the year because there usually is not enough heat from the sun to sustain the thunderstorms.