Howard County Sheriff Tom Busch says a tractor and sled went through the far end of the track, colliding with multiple vehicles, event staff and participants.
It happened shortly before 3 p.m. No spectators were in the area.
Investigators say it’s unclear what caused the tractor to malfunction.
The tractor was upside down on its side, according to one deputy.
All five victims were transported to St. Francis Medical Center. No names have been released.
By Brent Wiethorn, KKPR, Kearney