The disappearance of 27-year-old Jessica Boyce is now been treated as a homicide.
Boyce was last seen in Renwick on Tuesday, March 19, driving a red Holden Rodeo ute.
Police located her vehicle at the Lake Chalice car park in the Richmond Ranges on Friday, March 22.
They now believe her vehicle, which has been seized for forensic examination, was deliberately left in the car park in an effort to mislead the investigation.
Area investigations manager Detective Senior Sergeant Ciaran Sloan said: "As a result of their inquiries investigators have identified a number of other locations of interest in Marlborough.
"Additional resources from the Tasman and Canterbury Police Districts have been deployed to Marlborough to assist with the investigation, which remains a priority for Police.
"Police are committed to supporting Jessica's family throughout this investigation, and we extend our sincere condolences to them following this serious development."
Police again ask that anyone with information about Jessica's disappearance - no matter how insignificant they may think it might be - contact Marlborough Police on 03 578 5279, or Crimestoppers anonymously on 0800 555 111.