The 50-year-old was last seen walking along Wairere Rd about 11.30am on Monday.
Simpson was earlier described as being "mentally impaired" and usually only went out with the help of a family member or caregiver.
The three-day search involved police scouring the nearby area, including searching dense bush and carrying out an aerial search. Residents were also asked to check their security camera footage or dashcam footage.
The search had been made more challenging with the rural location.
Police said earlier that Michelle was last seen wearing a gold-coloured cardigan, a red floral medium-length dress and was possibly wearing a woven green/blue floppy hat. She was also carrying a patterned cream-coloured tote bag.
"It's possible she may have become lost and sought shelter somewhere," said Waitematā North area commander Bruce O'Brien.
He said the main focus of the ground search had been on the streets near where Simpson was last seen – Wairere Rd, Caton Rd, Gregory Rd and Horseman Rd.
The 50-year-old Michelle Simpson was last seen walking along Wairere Rd about 11.30am.