South Dakota Highway Patrol and other law enforcement agencies are warning drivers about possible suspicious activity on highways in the Pierre and Fort Pierre area.
In a post on Facebook on Thursday afternoon, highway patrol said drivers involved reported other vehicles attempting to stop them by boxing in their vehicles, flashing their headlights and using their hazard lights.
Authorities say they've increased patrols on the highways in the area and continue to investigate. Local law enforcement is also involved.
Highway patrol said drivers should not stop their vehicles or confront those involved if they encounter suspicious activity and should call 911.