Grace disappeared from Berrimah, in Darwin, on August 7.
Her mother, 34-year-old Laura Hinks – also known as Laura Bolt – is also sought.
Today, police confirmed a multi-agency task force had been set up to manage the investigation.
Detective Acting Senior Sergeant Jon Beer said the group that claimed to have allegedly abducted Grace continued “to peddle ideologies and false information that have no regard for the mental wellbeing of a five-year-old girl”, in the words of the police release.
“The [alleged] conduct of this group is despicable,” Beer said.
“NT Police will continue to target this group and any other persons assisting the ongoing harbouring of Grace.”
A 50-year-old woman was arrested in Darwin’s north in connection with the investigation on August 13.
She was charged with child abduction offences.