Queenstown Lakes District Council principal rural fire officer Gordon Bailey said the report confirmed the council's suspicions the fire started in three spots along the highway, just after the traction engines travelled through on March 16.
The resulting blaze took 11 helicopters and 70 people more than a week to extinguish.
"Investigators found coal deposits at the scene of three fires which started 3m-5m from the roadside and witnesses confirmed that the fires were starting in the wake of the steam engines, which could still be seen departing down the road," Mr Bailey said.
The report eliminated any other likely causes.
Mr Bailey said he had not spoken to the traction engine owners directly after the fire.
He would not name the owners or say where they were from.
Asked if the council would prosecute them or seek compensation, he said it was too early to say.
The report recommended costs be recovered where possible.
The council had made an application for costs to the National Rural Fire Authority Rural Fire Fighting Fund and was "hopeful" it would get the bulk of the $700,000 back from it.
However, "cost recovery" would also be explored, which would come down to a "matter of insurance".
Other recommendations in the report were that there was a need, when fire dangers were high, for fire authorities to be informed of intended travel of coal-fired engines; and there was a need for engine owners to be aware those machines needed to be well maintained so embers could not escape.
Mr Bailey said the recommendations were quite straightforward and agreed there was a need for the council to talk to Land Transport New Zealand with regard to coal-fired engines travelling around the district, particularly during restricted and prohibited fire seasons.
The Kingston Flyer vintage steam train, which takes tourists between Kingston and Fairlight, was considered a coal-fired engine and there had been problems in the past two summers with trackside fires started by embers from the train.
The train operators had been asked to clear plant growth around the track "for a certain distance either side", Mr Bailey said.
