The Telegraph reports that a 'credible' sighting leads to fears that the young girl was snatched by slave traders 10 years ago and sold in Morocco.
Former Scotland Yard detective, Colin Sutton told the Mirror that it was certainly possible that the little girl was abducted during the family holiday in Portugal and smuggled by ferry into Africa.
"If someone wanted to get a three-year-old child into Africa, it's the obvious route," he said "the infrastructure and contacts for people smuggling are clearly there."
If it's true, Madeleine could be alive somewhere in West Africa....
One link in 'The Mauritania theory' is a 'credible' sighting of young Maddie just days after she disappeared on May 3, 2007.
Mari Olli was vacationing with her husband when she spotted a girl 'identical' to Madeleine with a man at a gas station in Marrakech.
She told the Mirror that the little girl she saw was wearing blue pyjamas, looked "sad" and asked: "Can we see Mummy soon?"
Although she filed a report, no officers contacted her to follow-up.
"The Mauritania line is certainly a possibility and needs to be looked at," said Officer Sutton, "If someone wanted to get a three-year-old child into Africa it's the obvious route. The infrastructure and contacts for people smuggling are clearly there."
According to the Telegraph, gangs in Mauritania, West Africa are well known to sell young children to wealthy Middle Eastern families. It is unknown if police have already investigated this angle.
Read more about the Nanny's theory of what happened here. This investigator swears it was a murder and that Madeleine's parents are responsible.