Concerns are growing for an elderly couple, Patricia Pugh, 67, and her 70-year-old husband Robert, who disappeared from their home in Risca, South Wales, at 9.40am on Saturday.
Gwent Police say they are "extremely concerned" for the welfare of the pair because of their age and the ill health of Mrs Pugh, who is better known as Sarah.
The force said they are following up several lines of inquiry with other constabularies, including North Wales Police where the couple are believed to have links.
Mrs Pugh is approximately 5ft 2ins tall with blue eyes. She was last seen wearing a long dark padded coat. The couple are believed to be travelling in a silver Vauxhall Astra Estate, registration CA09 LFO.
Detective Chief Inspector Peter Jones said: "Gwent Police and the family of Mr and Mrs Pugh are extremely concerned about the whereabouts and welfare of Sarah and Robert.
"Every effort is being made to locate the couple. They are both considered vulnerable due to their age and it is imperative that they are located as soon as possible due to Sarah's ill health.
"I urge Sarah and Robert to contact police as soon as possible to let us know they are safe and well and appeal to members of the public to contact police immediately if they see the couple or the car they are travelling in."
Anyone with information is urged to call Gwent Police on 01633 838111.