A blizzard has blanked parts of the upper U.S. Midwest in thick snow, creating havoc among travelers, and causing damage to buildings.

The storm, which has hit Minnesota and Wisconsin the hardest, has so far not caused any injuries. But officials in Wisconsin have declared a state of emergency in dozens of counties.

A blizzard warning is also in effect for Chicago and parts of northern Illinois, Iowa, and other midwest states.

The National Weather Service says as much as 51 centimeters of snow fell in some areas. Chicago's aviation authorities have reported hundreds of flights were canceled at O'Hare airport and Midway airport.

Early Sunday, the inflatable roof of the Metrodome sports stadium in Minneapolis, Minnesota collapsed after 43 centimeters of snow fell in 24 hours.