Georgina Gharsallah's disappearance in Worthing a homicide case
A woman who disappeared nearly 18 months ago was probably murdered, police believe.
Georgina Gharsallah, 31, went missing "without a trace" in Worthing, West Sussex, on 7 March 2018.
"We are no closer to establishing the circumstances surrounding her disappearance", said police, who are now treating it as a homicide case.
New CCTV footage has come to light, which the force hopes may prompt people's memories of seeing her.
Images show two women walking along Chapel Road in Worthing around 16:00 GMT on the day Ms Gharsallah went missing.
Det Ch Insp Andy Wolstenholme said they need to identify the other woman in the footage.
He said it was "frustrating" as Ms Gharsallah seems to have "vanished without a trace", but somebody will know what happened to her.
"We have investigated many possible leads relating to Georgina over the past 18 months," he said.
"Sadly, I have had to consider the possibility that Georgina has come to harm at the hands of someone else, which is one of the hypotheses we have been working on.
"While Sussex Police continue to look for Georgina, and hope above all else that we can find her safe and well, I have taken the decision to record her disappearance as a homicide."
Ms Gharsallah, who has Arabian features and also speaks Arabic, is described as 5ft 2in (1.57m) tall, with shoulder-length dark hair, often worn in a top knot. She has a piercing above her left lip.
She was captured on CCTV in a phone shop with a number of mobile phones before she disappeared.
Two men were previously arrested on suspicion of her murder, but were later released with no further action.