Clue 1 ... eyewitness Karen Sisson saw Madeleine lookalike with German couple at Spanish campsite

DETECTIVES searching for Madeleine McCann are following up fresh clues from a potential sighting on Spain’s Costa del Sol.

A blonde girl identical to Madeleine was seen at a campsite there three days after she was snatched a few hours drive away in Praia da Luz, Portugal, on May 3, 2007. 

A witness said the groggy-looking child seemed alienated from the German family she was staying with in a caravan. 

Now Brit cops have been told the family paid extra for bringing one child more than expected when they arrived at the site on May 6.

And questions over the number plates on their car have raised fears they could have been fakes used to dodge detection.

Holidaymaker Karen Sisson, 49, who saw the child at the Cabopino campsite, near Fuengirola, said she got no response from cops when she raised the alarm at the time.

Clue 2 ... records show the family paid out to bring one more child than expected

Karen, of Gibraltar, said the girl wore a pink T-shirt, shorts and a beige hat and seemed “out of it”. 

She did not seem to fit with the German couple or their two curly-haired toddlers.

Karen said: “She seemed alienated and completely different to her family. It really was most peculiar.”

The mum of two said her suspicions grew the next day when she saw the girl wearing the same clothes as the day before.

Clue 3 ... German reg went out of use 38 years ago but car wasn't made before 1996

Karen left the day after, but the couple stayed two weeks. Campsite records seen by The Sun show they checked in under the name Karsten Mayer with a 1970 date of birth. 

Their car had a “BE” German plate, which went out of official use 38 years ago. Karen believes their car was a blue Mercedes Vito people carrier, first produced in 1996.  

Yesterday a source close to Madeleine’s parents Kate and Gerry McCann of Rothley, Leics, said the sighting had been passed on to Scotland Yard’s Operation Grange, set up to trace the youngster.

Fresh hope ... Kate and Gerry McCann

The McCann’s official spokesman said: “This lady has done exactly the right thing in reporting what she saw to police.”

Last month cops released a picture of how Madeleine might look now, at nine.