Detectives searching for a 46-year-old woman who has been missing for more than nine months believe she may have come to harm.
Patricia Henry has not been seen by her family since 13 November last year.
Ms Henry lived in Paisley, Renfrewshire, before relocating to Kirkwood Place in Girvan, South Ayrshire, last October.
Officers have now revealed they want to trace a large white van in connection with the inquiry.
The vehicle, which had a 66 registration plate, is thought to have travelled between the Glenburn area of Paisley and Ms Henry's new address between 15 and 16 November.
There have been no sightings of Ms Henry - who was formally reported missing in March - and no activity on her bank account or mobile phone since she disappeared.
Police Scotland said her passport had not been used and there was no evidence she had left the country.
Det Chief Insp Suzanne Chow, of the Major Investigation Team, said: "One line of inquiry that I now must consider is the possibility that Patricia may have come to some harm.
"It is really important though to keep an open mind to all lines of inquiry but the distinct lack of information about Patricia is concerning.
"I can't rule anything out at this time."
Detectives want to speak to anyone who spotted the white van on the 55-mile route between Ms Henry's former address in Burnfoot Crescent, Paisley, and her new home in the 48 hours after she was last seen.
They are also keen to establish if anyone in the vehicle was acting suspiciously.
As part of the inquiry the force's underwater unit and HM Coastguard have carried out searches in the Firth of Clyde, off the coast of Girvan, which is a short walk from Kirkwood Place.
On Wednesday officers travelled on trains between Paisley and Girvan, which is a route she used often, and spoke to more than 400 people.
Ms Henry, who is single and lived alone, is described as 5ft 10in, of slim build and with shoulder-length hair, which is usually tied back.
She has a tattoo of a red rose and green stem with a cloud in the background and the name "Patti" on her right arm and a tattoo of a dolphin on her hip.
Police said she usually wears a denim jacket.
Earlier this year, Ms Henry's daughter made an emotional appeal for her mother to get in touch.
Speaking at a police news conference, 18-year-old Alannah McGrory said: "Mum, if you see this please let me know you're OK."