(CBS News) As Scotland Yard talks to dozens of potential suspects in the abduction case involving British toddler Madeleine McCann, investigators say there is no proof that the three-year-old who disappeared in Portugal in 2007 is dead.
Police say categorically that the parents of Madeleine are not among those potential suspects. Kate and Gerry McCann are not speaking to the media, but a spokesman said they see this as a huge step forward in finding out what happened, and hope it will bring to justice those responsible for Madeleine's abduction.
The question of what happened to Madeleine McCann has remained unanswered since she vanished from a vacation home in Portugal six years ago.
She'd be 10 now. And British police are now saying there is every reason to believe she is alive. They've upgraded a two-year review into a full-scale, active investigation.
Metropolitan Police Service Chief Inspector Andy Redwood said, "Over the last two years, what the review has told me, is that there is no clear, definitive proof that Madeleine McCann is dead. And so, on that basis, I still genuinely believe that there is a possibility that she's alive."
Over the past six years there have been numerous reported sightings of Madeleine -- from Belgium, France and Spain, to Morocco, and even New Zealand.
This investigation identifies 38 potential suspects spread throughout Europe, 12 of whom are British.
Madeleine was nearly 4 years old when she disappeared without a trace while her parents were having dinner at a nearby restaurant with a group of friends.
Originally named as suspects, Kate and Gerry McCann have campaigned tirelessly in the search for Madeleine ever since, begging the British government for help after Portugal's investigation came up with nothing.
Those requests were finally answered by Prime Minister David Cameron, who ordered a review in 2011.
It's thought that known child sex offenders are among the 38 people identified in the new investigation.
After six years the trail has gone cold, but you only have to look at the case of the three women found in a Cleveland home a decade after they disappeared, or Jaycee Dugard, who was abducted as a child and kept prisoner for 18 years, to keep alive the the hope that Madeleine may still be alive -- and British police now have a renewed determination to find her.
Watch Charlie D'Agata's report above.