Madeleine disappeared from a holiday apartment in Praia da Luz in May 2007 when she was three years old.
But far from her kidnapping being a unique event, 30 youngsters under 18 have vanished since.
According to The Sun, it has also emerged that an abduction alert system introduced in 2009 for police and other law enforcement in Portugal has never been activated.
The news piles on more frustration for Madeleine's parents, Kate and Gerry, who have used the fifth anniversary of their daughter's disappearance to urge police to pursue the case.
Kate, 44, said on yesterday's fifth anniversary: "Abducted children have been found many years following their disappearance."
Last week, they issued a digitally-made photograph that shows Madeleine as she may looked now, at the age of nine.
It was also revealed yesterday that details of over 100 calls to Crimestoppers about Madeleine in the days after she vanished were never handed to police.
They mostly came from psychics. But Leicestershire cops said they were 'over-run' with information. Details of the calls have now been handed to Scotland Yard.
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