Police say speed may have been a factor in a fatal truck rollover on the state's East Coast on Monday morning.
Tasmania Police Acting Inspector Dean McMahon said the driver was very experienced.
"What we can eliminate is a medical condition and, at this stage, there doesn't seem to be any mechanical failure," he said.
"Wet weather didn't play a factor in it but speed may have."
There is a 45 km/h advisory speed sign in the area where the truck rolled over.
The truck was carrying heavy infrastructure to be used in constructing a bridge north of St Helens.
Tasmanian Police closed the Tasman Highway between Elephant Pass Road and just north of Bicheno for a majority of the day.
"It has caused major disruptions, because of the heavy infrastructure we've had to get a number of cranes in to clear the scene," Acting Inspector McMahon said.
The National Heavy Vehicle Regulator attended the scene along with police and Ambulance Tasmania.
Police have notified the man's next of kin.
Police would like to speak to the occupants of a white vehicle possibly travelling south and saw the truck near Picaninny Point.
Information can be provided to police on 6777 3936, or call Crime Stoppers anonymously on 1800 333 000. A report is being prepared for the coroner.