The landslide occurred at one o'clock on the night of Saturday and caused major damage to the E6 at Stenungsundsmotet.
About ten cars are said to have driven over the edge of the collapse. Three people were taken to hospital with minor injuries.
The road is destroyed in both directions and a large crack runs from one side of the road to the other and further into the landscape.
The E6 between Stenungsund and Ljungskile is completely closed and traffic is diverted via road 650. The assessment is that it will take a long time to repair the road.
The public is urged to stay away from the area due to the risk of more landslides.
According to experts, there is a lot of quickness in the area. Clay that can come into motion during rain or vibration, among other things. Mercury is found in large parts of West Sweden.
Watch the devastation in the clip below