The crashes were reported 16 minutes apart Saturday morning near the interstate's 83 mile-marker, police said.
The causes of the accidents are still being investigated, but police believe the second one occurred when drivers slowed down to look at the wreckage from the first accident, The (Louisville, Ky.) Courier-Journal reported.
The six people who died were in a SUV that caught fire after it was rear-ended by a tractor-trailer before noon, police said.
Two other people in the SUV suffered serious injuries, The Courier Journal said.
Fire trucks were still attempting to put out the SUV fire when four vehicles crashed across the road, leaving one critically injured.
The Courier Journal said the interstate, which was icy Saturday, was closed until 5 p.m. following the accident.