One lane of SH1 reopened around 3.45pm once the road had been hosed down by firefighters.
Kawakawa fire chief Wayne Martin said the cause of the fire, which appeared to have started in the engine area, was not yet known.
Dover Samuels, who passed the truck as he was driving home to Kerikeri, said the driver had to jump out as the flames took hold of the cab.
When he spotted the blaze the truckie had only just pulled over and the first firefighters had yet to arrive.
Another incident less than an hour later, also on SH1, created more traffic chaos.
About 3.50pm emergency services were called to a pile-up on the Three Bridges on the northern side of Kawakawa.
Martin said the three-car nose-to-tail crash occurred on the southbound lane of the middle bridge.
There were no serious injuries but the traffic delays were significant.
