A coffee service technician, Jeremy Batten, saw the glow from several kilometres away as he was driving to Kaitaia but thought it was a burnoff. Only as he drew closer did he realise it was a building.
"It was huge. The flames were a couple of storeys high."
A few minutes later the front of the building came crashing down onto the footpath. A woman was near hysterical, wrongly believing her children were inside, and had to be calmed by her partner, he said.
When Tautoko FM hit the airwaves in 1987 it was just the second iwi radio station in the country, the first to broadcast in FM and the first in Northland.
It is run by Te Whare Awhina o Te Iwi Charitable Trust, whose chairman, Hori Chapman, said they were saddened by the loss of history but already looking to the future.
"It could be seen as a setback, but we see it as a new start. We want to rebuild our whare and expand our services based around our vision," he said.
That vision included giving iwi a voice, improving well-being, and promoting te reo and tikanga Maori.
The station's archive, a treasure trove of recordings from Waitangi Tribunal hearings, had been moved into a container just a month earlier and was undamaged.
Mr Chapman said he was keen to rebuild in Mangamuka. It was not an urban centre but was central to much of the Far North. Many locals who had started at Tautoko FM had gone on to careers in TV.
The building was insured but any payout was unlikely to cover recent renovations. Trustees were considering a fundraising appeal.
Fire investigator Michael Champtaloup said the blaze had started at the rear of the building, possibly in the computer server room. He was yesterday still trying to pinpoint the cause.
The blaze showed just how fast fire could spread, he said. When a shop owner called 111 it was still relatively small but when the first firefighters arrived from Okaihau 23 minutes later the entire building was consumed by fire. It would have been deadly to anyone inside within five minutes, he said.
The building was not fitted with smoke alarms.
"Alarms might have picked up the fire early enough to save the building. It was an important building to the community and they've lost a lot of history."
Fire Service volunteer support officer Colin Kitchen said three appliances and two tankers from Okaihau, Kaitaia, Kohukohu and Kaikohe responded. Twenty firefighters in breathing apparatus took about an hour and a half to put out the fire.
The volunteers did a great job of saving the adjacent buildings, Mr Kitchen said.
The building was originally part of the Motukaraka dairy factory in North Hokianga. It was barged up the river and later became a farming supply store.
* Police are also trying to determine the cause of the fire. If you saw anything unusual in the area of the radio station on Monday evening, call Detective Sergeant Chris Fouhy at Kaikohe police on (09) 405 2960 or Crimestoppers, anonymously, on 0800 555 111.