Detectives searching for the body of Emma Faulds have said the movements of two black cars are central to their investigation.
They have appealed for mobile phone and dashcam video of a black Mercedes and a black Jaguar car.
The vehicles are known to have been on the A714 Girvan to Newton Stewart road – the Mercedes on Monday 29 April and the Jaguar on Tuesday 30 April.
A man has been charged with Ms Faulds’ murder.
Ross Willox, 39, made no plea at Ayr Sheriff Court and was remanded in custody.
Ms Faulds, who was 39 and from Kilmarnock, was last seen in Monkton in Ayrshire on Sunday 28 April.
Police have said their operation includes specialist search advisors and forensic officers.
The Police Scotland force helicopter is also being used to assist with mapping the area.
Det Ch Insp Martin Fergus, who is leading this inquiry, said: “What Emma’s family is going through is unimaginable and our priority is to find her.
“I am thankful to members of the public who have been in touch and have provided us with valuable information which has led us to explore this area.
“I believe the A714 route is key to helping us find Emma and I am appealing again to those who use this route regularly, please take time to think back and consider if you saw a Mercedes or Jaguar car on this road or parked up somewhere, or even off road.
“If you have dash cam footage, please take the time to go through and check it.”
He added: “You may not realise it but you could have captured footage of the vehicles in these locations which could provide us with vital information and assist us in finding Emma.”