Highway 109 at Clayton Road is back open after a serious crash in St. Louis County.

Police responded around 11 a.m. to a two-vehicle head-on crash.

A pick-up truck was traveling southbound on Highway 109 when it struck a small SUV that was traveling northbound head-on. The driver of the SUV, a 63-year-old woman, was listed in critical and unstable condition and the driver of the pick-up truck, a 56-year-old man, was in stable condition with serious injuries.

The incident is under investigation by the St. Louis County Police Department’s Bureau of Crimes Against Person and Accident Reconstruction Unit. Investigators are investigating the possibility that the driver of the truck suffered a medical emergency.

The road opened back up at around 3:35 p.m.