Severe thunderstorms have raked parts of the Midwest, spawning at least one tornado that damaged several homes in Reno township, Kansas.
The twister also sent race fans fleeing, snarled air traffic and knocked out power.
The tornado touched down in southern Leavenworth County in Kansas, northwest of Linwood.
Storms packing hail and lightning led the Kansas Speedway to suspend the NASCAR truck race 52 laps into the race.
About 30 minutes after the race was called, tornado sirens went off at the track and a local TV station showed a twister on the ground to the southwest. Most of the fans had already left by then, but others sought cover.
Thunderstorms rolling through northeastern Illinois caused about 100 flights cancellations at O'Hare International Airport in Chicago and delays of more than two hours, according to the city's Department of Aviation. Flights were delayed about an hour across the city at Midway International Airport, but no major cancellations were reported.
Storms packing winds of up to 80 mph brought down power lines in southern Michigan, leaving about 123,000 homes and businesses without electricity.