It is feared Margaret was killed or died naturally and her remains were dumped. Specialist police units have already used dogs, a helicopter and divers to search woodland, undergrowth and water for her body.
A senior detective said last night: "This poor girl has failed every proof of life test we use to establish whether or not someone is deceased.
"Everything is pointing to Margaret being dead. There has been nothing - no GP appointment, social worker, job, social life or friends - to indicate that she may be alive."