A forensic expert has shared his three theories behind the "very credible" evidence that may have led police to search for Madeleine McCann this week.
The first searches in nine years for the British girl who vanished in 2007 from Portugal have taken place after German police received "credible" new information.
Officers have been extensively searching the surrounding area of the Arade dam, about 30 miles from Praia da Luz, where Madeleine was last seen alive just before her fourth birthday.
