Police are still learning what caused a five-vehicle pileup near Hampshire Wednesday that left eight people dead.

Charges are pending against the driver of a semi-trailer that collided with a tour bus Wednesday afternoon. It happened near the Marengo toll plaza on Interstate-90.

Investigators are interviewing the truck driver and studying the wreckage.

Police say the collision with the tour bus was the first in a chain reaction accident involving two other semi-trailer trucks and a pickup.

The tour bus was taking members of a women's group back to Chicago. They had been in Rockford to visit the Anderson Japanese Garden.