Emergency services were called to the blaze 3km south of Hay on the Cobb Highway.

The highway was closed in both directions as firefighters fought to extinguish the blaze.

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A video taken at the time shows the road train fully engulfed with flames against the darkness of the early morning while firefighters battle to bring the blaze under control.

While the truck's driver and sole occupant escaped uninjured, unfortunately the same could not be said for the road train and its load of cotton, which were destroyed in the flames.

Fire & Rescue crews from Hay and Griffith remained at the scene until late Wednesday afternoon and authorities on the ground requested an excavator to pull the truck apart for the clean up.

Police, Ambulance, Hay RFS and Roads and Maritime Services also attended the scene.

A Fire & Rescue spokesperson said the load of cotton is expected to keep burning for quite some time.

"The cotton will probably continue to smoulder for a couple of days until it can be recovered," the spokesperson said.

Despite this, Fire & Rescue have reassured members of the public who may see it smouldering on the roadside that everything is under control.

"It's not a threat and Fire & Rescue crews are continuing to monitor it," the spokesperson said.

The highway reopened late Wednesday morning and a reduced speed limit and alternating traffic conditions remain in place.