The British expat, George Burke said he saw a girl who looked "remarkably like Madeleine" being dragged along a road leading to Lagos marina at 6am on May 4th.

Although Burke reported the sighting to Portuguese police at the time, it has taken until now for his account to be taken seriously, according to the McCanns' private detectives, Metodo 3.

Madeleine McCann: The new sighting coudl mean that she was kidnapped and then taken by sea

Mr Burke, who is originally from Liverpool but now lives in Portugal, said he saw the suspicious couple as he drove past the marina early on the morning after Madeleine went missing.

He told the Daily Mirror: "It was very, very dark and it was hard to make out exactly what the couple looked like. But through the gloom I could see a very suspicious-looking man and woman, with a child who fitted Madeleine's description.

"Though there was nobody else on the road, they were hurrying across a road that leads straight to the train station and marina."

Police search the marina shortly after Madeleine's disappearance

The McCanns have said in the past that they believe that their daughter was taken by sea, possibly to Morocco or elsewhere in North Africa.

A source said: "The private investigators are now concentrating on Lagos and the marina.

"What Mr Burke saw could be incredibly valuable.

"He was concerned enough to call the police and they eventually followed up on his information.

"Now the investigators want to talk to Mr Burke. There is a strong chance Madeleine was taken by boat from the marina and is still alive somewhere."