Emergency services are at the scene of a serious crash on the Dukes Highway, near Tailem Bend.
The collision occurred about 500 metres north of the Mallee Highway intersection, south of the Tailem Bend township.
The Dukes Highway is closed to traffic in both directions and motorists are advised to avoid the scene if possible.
Major Crash investigators are making their way to the scene.
Anyone who witnessed the collision who was not able to stop at the scene can provide their details via Crime Stoppers on 1800 333 000 or online at www.crimestopperssa.com.au