It comes as her parents Kate and Gerry (pictured) were said to be 'greatly encouraged' that Scotland Yard could finally be closing in on Maddie's kidnapper after eleven-and-a-half years.
It comes as her parents Kate and Gerry (pictured) were said to be 'greatly encouraged' that Scotland Yard could finally be closing in on Maddie's kidnapper after eleven-and-a-half years.
Madeleine McCann could still be alive and trapped in an underground dungeon, a retired detective who investigated her disappearance has claimed.
David Edgar believes Maddie could resurface 'at any time' and likely has 'no idea' about her true identity, having probably been abducted by a child sex gang.
The investigator,who worked on behalf of Maddie's family for three years, also suspects that she might still be in Portugal, where she vanished from in 2007.
It comes as her parents Kate and Gerry were said to be 'greatly encouraged' that Scotland Yard could finally be closing in on Maddie's kidnapper after eleven-and-a-half years.
The Home Office last week announced it would grant an extra £150,000 to Operation Grange to keep the investigation going until spring next year.
So far they have handed out £11.75 million of taxpayers' money for the high-profile search, with officers looking into two vital leads.
Mr Edgar said officers could be looking into his own theory that Maddie was taken by a paedophile ring and that whoever was responsible may have confided in someone.
He said: "I've always thought that whoever is responsible will have confided in someone else. They usually do and it is very rare that they don't even if it takes years.
"Now we're approaching the 12th year, that's a significant time but I think she could still be alive and someone is protecting her captors.
"Someone knows what happened and it's time they came forward, maybe they have and officers are waiting for a confession. It happens."
It comes as her parents Kate and Gerry (pictured) were said to be 'greatly encouraged' that Scotland Yard could finally be closing in on Maddie's kidnapper after eleven-and-a-half years.
Mr Edgar added: "She could literally be anywhere in the world but my hunch is that she is in Portugal. The chance that she may have been smuggled out of the country without being detected is highly unlikely.
"There is someone in Portugal with an open knowledge of where she is and what happened. Someone knows what happened and it's time they came forward - maybe they already have."
"Unless a body is found there is hope. Everyone hopes for a positive outcome and Kate and Gerry will never give up, even when the funding runs out. I hope they get an answer they've been waiting for so long."
Mr Edgar believes Maddie - who if alive would now be aged 15 - could be living with her captor in a hideaway home or underground den inland from the popular seaside towns on the Algarve from where she was snatched.
He likened her case to that of kidnapped sex slave Jaycee Lee Dugard who "came back from the dead."
David Edgar (shown) believes Maddie could resurface 'at any time' and likely has 'no idea' about her true identity. Photo / Getty
The 11-year-old schoolgirl was abducted from a street in Tahoe, California, in June 1991, on her way to school and was kept imprisoned for 18 years. She was found alive in August 2009.
Mr Edgar said: "There is every possibility that Madeleine is still alive and could be being hidden somewhere and having no idea even who she is and that she is at the centre of a worldwide hunt for her.
"He said the vast wilderness where he believes the teenager could be languishing may be almost impossible to search completely.
He explained: "This rural, sprawling terrain makes it extremely difficult to search. You could quite easily keep a child there for years and no-one else would know.
"She could be hidden away in a cellar or dungeon in the lawless villages around the resort she went missing from. The key thing is no body has been found.
"When paedophiles kill they often dump the body nearby and this doesn't appear to be the case here. Even the ocean often gives up his victims."
An image of what Maddie McCann could look like as a young teenager. Photo / Supplied
Maddie vanished from a holiday apartment in Portugal's Praia da Luz eleven and a half years ago just days before her fourth birthday.
She had been left alone sleeping with her younger twin siblings while her parents were dining in a nearby tapas restaurant with pals.
Police recently told her parents: "We're hopeful we can get a result." Op Grange team, who had been thought to be focusing on just one, told Kate and Gerry during a meeting they had 'two specific and active' lines of inquiry.
The McCanns are "greatly encouraged" that cops could finally be closing in on their daughter's kidnapper.
It is understood detectives met Kate, a former GP, and eminent cardiologist Gerry, both 50, at their home in Rothley, Leics, last month.
Police refuse to make public any clues about the suspects they are determined to track down for fear of them going to ground.
Mr Edgar said the new funding was "totally justified." He said: "It's a very delicate case but officers would not have requested extra funding if they didn't need it.
"Whether they'll crack it, it's impossible to say but everyone hopes there is a positive outcome.
"I think there will be a resolution, it will be something simple like someone talking - a confession is the best hope of a breakthrough."
Madeleine McCann (pictured) could still be alive and trapped in an underground dungeon, a retired detective has claimed.
A Scotland Yard spokesperson refused to discuss the two leads they are actively chasing, saying: 'We cannot give a running commentary while there is an ongoing investigation.'
Mr Edgar, who has had more than 30 years experience with Cheshire Police and the Royal Ulster Constabulary, stopped working for the McCanns when the Met Police came on board in May 2011 on orders of then Prime Minister David Cameron.
He added: "I firmly believe this case will be solved eventually - it is not beyond the realms of possibility."
