A 40-year-old man was found dead in the cabin of his truck at a rest stop near Hillston on Friday.
Police are not treating the death as suspicious.
Griffith police have launched an investigation into the death of the man, a Victorian truck driver, who was found by a passing motorist about 5.30pm.
The Mack truck was laden with sheep when it was found at the rest stop, on Kidman Way and Monia Gap Road, about three kilometres from the town.
A post mortem is scheduled this week to determine the cause of death.
A report will be prepared for the coroner.
Police would like to hear from all witnesses who observed the truck and the deceased driver.
Griffith police Inspector John Wadsworth said the inquiries into the death of the man were ongoing.
"We're still trying to piece together what happened," Inspector Wadsworth said.
Any witnesses can contact Griffith police on 6969 4299 or Crime Stoppers on 1800 333 000.