Seven vehicles were involved in an accident on I-84 westbound just after 5:30 Wednesday.
Idaho State Police said the driver of a semi truck failed to slow for traffic stopped ahead of him and smashed into a 2015 Subaru Impreza, setting off a chain reaction.
5 other vehicles were involved in the collision.
Four people were transported to the hospital. Their injuries are unknown at this time.
Three lanes were blocked for hours while crews worked to clear the scene.