A grieving whānau taking their rangatira's body to his tangi were caught in a serious car crash after a detour forced them to take a road they would not otherwise have travelled.

It has brought criticism of the state of the road network in the "forgotten" Far North where millions of dollars of damage has been wrought on the roading network after weeks of heavy rain.

One person was critically injured in the crash which happened just north of Taipa on State Highway 10, on the east coast of the Far North.

The injured person was the driver of a white Honda which is believed to have crossed the centre line at the brow of a hill, striking another car head on before cascading about 60m along the road striking multiple vehicles as it went.

Among those was the convoy of vehicles bringing the body of Keith Tobin to Te Paatu Marae south of Kaitaia. Normally, those travelling to Te Paatu marae would have crossed the Mangamuka Range on SH1 to where it sits at Pamapuria.

That route is closed with the main highway again blocked just 10 months after a year-long closure. The earlier extended closure was brought about by slips which made the route impassable. Recent heavy rains have brought a fresh series of slips.

Mangonui chief fire officer Mark Donnelly said the brigade raced to the crash scene about 6.30pm on Friday and were greeted by what appeared to be "carnage".

As it turned out, he said the immediate impression of a string of damaged vehicles and people milling about made it appear worse than it was.

He said the fire crew identified two people needing medical help - the driver of the car which appeared to have crossed the centre line who was trapped in his car with serious leg and chest injuries.

The other person was the driver of the vehicle he had struck head on. Donnelly said the woman driver, who was pregnant, and her child were effectively saved by airbags in a car only two weeks old.

From that initial impact, Donnelly said the car continued along the road striking multiple vehicles before rolling and coming to a stop. "We had to cut the guy out of his car."

A sole St John ambulance responded and set to work stabilising the driver as a helicopter waited. With no second ambulance available, the family of the pregnant woman took her to Kaitaia Hospital after she expressed concern for her unborn child. By the time she left she had felt the baby kick, said Donnelly.

Kaitaia deputy fire chief Ross Beddows, whose brigade turned up to support the Mangonui crews, said: "How no one was killed was a bit of a miracle. Amazingly, no one else was badly hurt."

One of the five slips identified at the Mangamuka Gorge.

The accident caused the official detour route along SH10 to be closed until at least midnight, creating a long line of traffic but also bringing displays of community spirit.

One local posted to social media an offer of fish pie and Milo for anyone caught up in it. The person offered directions to their house and asked people to sound their car horn at the gate if they were after a hot drink and something to eat.

Far North councillor Felicity Foy of Kaitaia said it was becoming apparent that resilience and infrastructure planning for the Far North roading network had not been done.

She said the closure of the SH1 route over the Mangamuka Range was a particularly difficult blow coming so soon after it was closed for a year.

Foy said the slips which led to the last closure had been exceeded by the current damage which had yet to end with unstable earth yet to settle. Aside from damage on the national roading network, there was $7m damage to local roads.

She said the official detour on SH10 included travel across two bridges which need replacing. One bridge required heavy vehicles to travel across at 10km/h using only the centre and another had speed restricted to 50km/h.

"One of the real sore points is the condition of SH10. I'm not sure what's going to happen when those bridges fail."

Foy said one of the frustrations was not knowing when the damage to SH1 was going to be resolved. She said she was pleased Marlborough was getting the support it needed after recent heavy rain but help was also needed in the Far North.

"People are really at their last tether. Why aren't we important? Why are we being forgotten?"

Waka Kotahi regional manager Jacqui Hori-Hoult said SH1 was a "vital economic lifeline for Northland" and the agency was committed to keeping it dependable and resilient.

Fulton Hogan supervisor Kevin George and Waka Kotahi's Jacqui Hori-Hoult at the reopening of the Mangamuka Gorge in June last year.

She said the increasing frequency and intensity of severe weather events brought on by climate change meant slips and closures were more common across the country and its roading network.

Hori-Hoult said the full extent of the damage at multiple locations through the Mangamuka Gorge was still being assessed. Decisions on repairs and reconstruction would follow that work, she said.

She said assessment work had to be carried out carefully for the safety of workers "with the ground conditions in the gorge still highly unstable in places".

"We understand that the community is anxious to hear about the next steps forward, and we are keen to provide more information as soon as we have it."