A man has been killed in a single vehicle crash on the Arthur Highway in the state's south-east.
The 42-year-old man was driving a truck carrying chickens about one kilometre north of Eaglehawk Neck when it rolled over about 5.30am.
He was confirmed to have died after 9.30am.
The man's passenger was taken to hospital with non-life threatening injuries.
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Investigators will remain at the scene throughout Monday morning and are seeking to speak with the driver of a white Toyota Corolla, or similar, which was travelled towards Eaglehawk Neck just prior to the crash.
The driver is asked to contact police.
A man, described as tall with a beard, was also believed to have witnessed the crash and is being asked to contact police.
One lane of the Arthur Highway is open, but the road will be closed for several hours from 10.30am to allow the scene to be cleared and for investigations to continue.
Anyone with information about the crash can contact Crime Stoppers on 1800 333 000.