Alyssa Barker was taken from her home near Kaukapakapa yesterday afternoon by a family acquaintance, 27-year-old Skye Mason.
The pair were seen at a property in Glen Eden at about 10pm last night, but there have not been any reported sightings of them since.
Detective Inspector Stan Brown said the passage of time, the overnight temperatures and the fact that Ms Mason had no home to go to was of great concern with regard to the welfare of Alyssa.
"Having said that, the people who saw them last observed that Skye was caring for Alyssa as if she were her own child.
"Skye has had a short acquaintance with Alyssa's parents who are obviously very distressed their daughter has been taken from her home."
Police, including the Specialist Search Group (SSG) and the Air Support Unit (Eagle), searched in the Glen Eden area overnight until they were stood down at 3.30am.
Detective Inspector Brown said it was vital that anyone who has seen or had contact with Skye Mason or Alyssa Barker since yesterday afternoon and particularly since about 10pm last night, called 111.
The police search operation was back underway today with SSG back in the Glen Eden area and Eagle had again been requested to help.
Northern police spokeswoman Noreen Hegarty told APNZ Alyssa's parents were "understandably frantic".
"It's very important that we get reported sightings of one or both of these people so we can find Alyssa."
Alyssa is described as a stocky child with sandy blond hair and blue eyes. She was wearing pink and white striped pants, a green and white T shirt and gum boots.
Ms Mason is described as Caucasian, 160cms tall, and of slim to medium build with golden-brown long hair. She was last seen wearing black addidas pants, a pale blue shirt with dark patterns, gloves, and white addidas shoes.
- Rebecca Quilliam, APNZ
