A truck driver was unaware his moving trailer had been engulfed in flames until he heard a loud explosion and looked in his rear-view mirror.
Firefighters received multiple calls from vehicles travelling behind the truck after its trailer caught fire on State Highway 3, north of Palmerston North, shortly after 7am today.
NZ Post spokesman Michael Tull said the driver of the Roadstar truck had only become aware of the fire after hearing an explosion.
"The driver heard a loud bang from behind him, or a number of bangs. He looked into he mirror and saw that the trailer was on fire,'' he said.
"The driver stopped and got out. Nobody was injured.''
The man disconnected the trailer unit leaving it to burn.
Fire Service central communications shift manager Murray Dunbar said there had been multiple calls about the fire from vehicles which were also on the road.
"They looked in their wing mirrors and saw it and it pulled over.''
Firefighters battled the blaze that saw aerosols cans explode into the air shortly before their arrival.
Constable James Bennett confirmed the two occupants of the truck escaped unhurt. No other vehicles were involved.
Police put cordons in place while the road was being cleared of debris. A crane was being used to remove the units.
Mr Tull said while the truck had Courier Post branding, it was actually carrying commercial freight for sister company Roadstar, rather than individual courier packages.
The freight was mostly made up of paper goods like tissues and paper towels, as well as a small quantity of aerosol products, which had exploded when they heated up.
About three quarters of the freight had been destroyed.
Mr Tull said an investigation was yet to establish the cause of the fire, but it was initially thought to be mechanical in origin.