Fire and Emergency Services will not be prosecuting anyone regarding the Tangoio fire which razed more than 400 hectares of young forest land.
The investigation report released to Hawke's Bay Today under the Official Information Act stated the most likely cause of the January 6 blaze, that took 11 days and 300 people including volunteer firefighters and forestry staff to stem, was a faulty bulldozer exhaust.
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Fire and Emergency Services' region manager Bruce Stubbs said as an organisation the priority was to educate New Zealanders about the risks associated with fire.
"While we have the ability to prosecute, for this fire we are undertaking an educational approach," Stubbs said.
"With forestry being a key partner of Fire and Emergency New Zealand and a substantial industry around Hawke's Bay and Gisborne, we want to work with industry leaders to minimise potential fire risks."
On Friday K & S Beard Logging owner Kerry Beard, which had the faulty Komatsu D65EX-12 bulldozer on-site, told Hawke's Bay Today he was happy there would be no prosecution but did not comment much further.
"I am meeting with Forest Management NZ about the report and I do not have any further comment to make until then."
The fire in Tangoio Forest, off Tangoio Settlement Rd, was reported to the Fire and Emergency Communication Centre at 11.43am.
It eventually burned through 195ha of one to five year old trees as well as pasture and scrub and destroyed or damaged an estimated 500 metres of boundary fence.
Beard previously said he was under the impression the fire was caused by a cigarette butt.
"The wind was blowing so hard that day the fire definitely did not start from a spark from the bulldozer."
He stated he was surprised by the findings but stated he could not argue with them.
"We'll definitely get the exhaust fixed on the bulldozer, and get the bulldozers cleaned out."
The report's key evidence came from a mechanic who inspected the bulldozer on January 15, nine days after the start of the fire.
The mechanic found the exhaust system was in generally poor condition with a metal band partially covering a hole in the exhaust pipe.
There was evidence of exhaust gas leakage around this hole, with an area above the can blackened.
He also carried out a spark arrester test.
A spark arrester is any device which prevents the emission of flammable debris from combustion sources, such as internal combustion engines, fireplaces, and wood-burning stoves.
The machine failed the spark arrester test with more than 50 burns from carbon in the tester.