The wreck shut down the northbound lanes of I-29 north of Platte City.
Two semi trucks and at least three vehicles were involved.
Troopers say Jerry R. Wofford, 65, was taken to Heartland Regional Medical Center where he is being treated for serious injuries and Robert J. Sanko, 45, was taken to North Kansas City Hospital where he is being treated for moderate injuries.
Robert A. Dixon, 42, Debra L. Nichols, 55, and Willie E. McIntosh, 53, were all treated for minor injuries. Richard R. Fox, 43, was involved in the accident but not injured.
According to troopers, Sanko, Dixon, Nichols, McIntosh and Fox were all wearing their safety belts, while it is unknown if Wofford was wearing his.
Robert Sprague lives near the crash site and has seen multiple accidents in the area.
"People get comfortable with the drive from St. Joe into Platte City and traffic gets congested," he said. "People just forget what they are doing."
The highway was closed late into the night.
Troopers are still investigating the cause of the crash.