Hawke's Bay lines company Unison Networks is facing potential legal action on two fronts over a spate of wildfires that destroyed homes and property near Waimarama Road last year.
Power lines colliding in high winds were suspected of causing the devastating fires January and February 2017, though Unison denies it was to blame.
RNZ understands a fire investigation report completed more than a year ago concluded the fires were caused by Unison's power lines, but Fire and Emergency is refusing to release the findings.
"Fire and Emergency considers the release of this information would likely prejudice the maintenance of the law, including the prevention, investigation, and detection of offences, and the right to a fair trial," Fire and Emergency director Leigh Deuchars said in a letter.
However, Unison confirmed to RNZ that it was now facing potential legal action from Fire and Emergency.
"Fire and Emergency allege that Unison is liable to it for a significant loss. Unison denies it is liable. However, as it is possible that Fire and Emergency will file legal proceedings against Unison, it is inappropriate for Unison to comment further on the fire at this time," spokesman Danny Gough said.
The costs were understood to be just under $1 million. The Forest and Rural Fires Act 1977 provided a mechanism to recover costs from the person or people responsible for fire outbreaks.
Separately, a group of residents were also considering legal action against Unison to recover the costs of uninsured property lost during the fires.
Some of that property included forests and dwellings.
The first major fire started at Hawke's Bay farmer George Lyons' front gate, on Ruakawa Rd near Hastings, on 22 January. It burned through 15ha of farmland and severely damaged his house.
Witnesses described seeing power lines arcing in the wind, showering sparks onto dry grass which caught fire.
On the worst day of three weeks of wildfires, crews called in from across the country battled seven separate fires. A state of emergency was declared on 13 February 2017.
At the time Unison said its power lines could not have started the fire, because none of its systems picked up an outage at the time the fire began.
The company refused to release what are known as tripping logs for that day to RNZ, saying an investigation was underway and it could not comment further.
But several witnesses said that on the morning of the fire there was a power cut of at least 20 minutes. Power lines run directly over the area where the Waimarama Road fire began.