The police in Waikato say pathology reports indicate a woman found on fire was alive when she was set alight.
They say the reports show the cause of her death was the fire.
The body of the woman was found burning on the side of an isolated rural road west of Huntly on Thursday evening.
Police say they believe they have been able to identify her, but it is still too early to release her name.
Tests are being done to identify what sort of accelerant was used.
Police are asking for sightings of any vehicles or people on Hangapipi or Rotowaro Roads between 9pm and 10.30pm on Thursday or reports of anything untoward.
Police say people should also come forward if they find discarded clothing or other items in the area.