Linda Frances Sidon was last seen in June 2009.
The 53-year-old lived on the Gold Coast in a state house with her son Daniel. She was born and raised in New Zealand, but moved to Queensland in the 1980s and Daniel was born there.
In 2010 her South Island-based father contacted the Dunedin police and reported her missing. The report was passed to police in Queensland and until recently she was considered a missing person.
They said "fresh information" led them to believe she had "met with foul play".
Daniel (28) was named as a suspect as police and specialist search teams carried out an exhaustive search of bushland near the home he shared with his mother.
Cadaver dogs were used and digging equipment was brought in to excavate areas of bushland.
Today Gold Coast regional crime coordinator Detective Superintendent David Hutchison refused to say what had been found in the search - or give any specifics on the investigation into Ms Sidon's disappearance.
"The investigation into the disappearance of Linda Sidon is continuing," he said.
"Further searching may occur in the area of bushland at some point in the future. We are not releasing the results of the search so far."
He said Daniel had not been charged at this stage but would not elaborate on why police believed he was a suspect.
"He is still residing in Queensland. He has cooperated with previous interviews with police," Mr Hutchinson said.
"No further information is being released at this stage regarding the investigation."
