A Fire and Emergency New Zealand spokesman said two crews were attending a truck fire on Thames St near the intersection with Nen St.
They were notified about 5.50pm.
A third crew was notified but had been stood down.
The crews in attendance were putting out the blaze with water and there were not believed to be any hazardous goods at the scene.
Initial reports of an explosion were now thought to be a tyre bursting.
A nearby resident said she heard a loud bang from inside her house and went out to investigate.
She saw billowing black smoke and some smaller flames.
Some people were trying to fight the blaze with fire extinguishers before the fire department got there, but they were unsuccessful and the flames took off.
The truck appeared to be carrying rubber pipes, she said.
