Christchurch police want to speak to two people in a car seen on a road before missing woman Emma Campbell's car was found.
Ms Campbell was last seen at a Riccarton Rd service station early on the morning of 1 May. Her car was first noticed down a bank on Dyers Pass Road about an hour and 40 minutes later.
Detective Senior Sergeant John Rae says a woman driving down the road between the two times saw a light-coloured car, with two occupants, reversing.
Because it was dark, however, the witness has been unable to identify the make and model.
In another development, Mr Rae says images of a car similar to Ms Campbell's caught on CCTV on Colombo St will be enhanced to confirm if it was hers.
If it was, he says, that would fit with the direction in which she must have driven to get to Dyers Pass Road. The time it was photographed also means that the car must have been elsewhere before it travelled along Colombo St.
Mr Rae says the case is frustrating, as all areas Ms Campbell may have gone have been searched. The search has been wound down but anyone with information about Ms Campbell's whereabouts - and there must be someone, Mr Rae says - is urged to come forward.