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(CNN) — Three people were killed Thursday in a 30-vehicle pileup on Interstate 94 in northern Indiana during whiteout conditions, according to state police.

More than 20 people were sent to area hospitals, including one person with life-threatening injuries, according to Sgt. Ann Wojas of Indiana State Police.

LaPorte County was experiencing heavy snow and extreme cold and winds.

Police said half of the vehicles were tractor-trailers.

Police Lt. Pete Wood said it could take 12 to 24 hours until things get back to normal on I-94. Motorists were urged to find alternative routes.

By Susanna Capelouto

CNN’s Carma Hassan contributed to this report.