Watch: Truck becomes an inferno on Napier-Taupō Rd

State Highway 5 between Napier and Taupo has been closed for at least the sixth time this year and the 17th time since the start of 2021 following a multiple-vehicle crash just hours after a truck was destroyed by fire in another incident on the road.

The fire was reported near Te Haroto just after 3am, and seven fire crews and trucks were involved in battling a blaze that kept some busy until after 7am.

The multiple-vehicle crash happened about 12.45pm between Te Pohue Loop Rd and Richmond Rd, with police national media staff telling Hawke's Bay Today it had been reported initially three cars had been involved, one appearing to have been towing a caravan.

One person was initially described as seriously injured and one motorist at the scene said there were "cars everywhere".

National highways management agency Waka Kotahi NZTA reported the road was reopened by 4pm, but police said there were still "long tails" of traffic.

Waka Kotahi told Hawke's Bay Today on Thursday there had been 11 Napier-Taupo closures of the highway last year and five up to what had then been the most recent, on Tuesday this week, with causes including crashes, fire, snow, fallen trees and other factors.

Meanwhile, a woman who witnessed the fiery explosions engulfing the trailer of a truck on the Napier-Taupō Rd has praised fellow truckies on the highway for their response.

Angela Payne was parked near the summit of the road when she was woken by the sound of explosions.

She saw the truck's trailer on fire and other trucks around the scene, with people trying to help.

"The truck drivers were the heroes .... They managed the scene and helped keep each other safe," she said.

Angela Payne witnessed explosions and then big flames engulfing a truck on SH5. Photo / Angela Payne

Payne said she was told there were dangerous goods on board and that the trailer brakes had overheated.

Seven fire trucks were sent to the scene of the fire, a Fire and Emergency NZ spokesperson said.

All had left by 7.10am.

A police spokesman said they were notified but weren't required at the scene.