Montgomery County, Illinois - At least six people were killed and more than 30 injured after a dust storm caused pileups from vehicle crashes and a shutdown of Interstate 55 Monday morning, according to Illinois State Police.

State police troopers responded to "numerous crashes" about 11 am Monday on northbound and southbound I-55 near milepost 76 in Montgomery County, south of Springfield, police said.

About 20 commercial vehicles and 40 to 60 passenger cars were involved in the crashes, according to preliminary information, including two tractor-trailers that caught fire.

The crashes were caused by "excessive winds blowing dirt from farm fields across the highway leading to zero visibility," police said.

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I-55, the major cross-country, north–south route connecting LaPlace, Louisiana, to Chicago, was shut down in both directions from milepost 63 to milepost 80, according to Illinois State Police.

"Visibility in the area is reported to be low due to blowing dust," the agency said in a written statement. "Traffic is urged to seek alternate routes."

At 8 AM EDT, state police issued an update on Twitter, saying "Interstate 55 around milepost 76, both northbound and southbound, opened around 6 AM."

Investigations into Monday's incidents continue.