As many as 20 vehicles were involved in a fiery pileup that stretched for miles on I-57 near Peotone, Ill., southwest of Chicago. Low visibility caused by dense fog was a factor, authorities said.

At least 12 people were injured, but all of them are expected to survive, Chicago's WLS-TV reported. On Thursday afternoon, five accidents were reported in the northbound lanes of I-57 near Peotone, and two in the southbound lanes.

State police closed a six-mile strech of the road for hours. All lanes were reopened by 11 p.m. Thursday.

Authorities say the crash involved seven semi-trailer trucks. At least one of the trucks caught fire after the crash. One vehicle was trapped beneath a semi. Extrication equipment and cranes were brought to the scene by emergency crews.

(MORE: Live Updates on Severe Weather)

Illinois was in the middle of a massive weather system brought blizzard conditions to the Upper Midwest and reported tornadoes into the Tennessee and Ohio Valleys.