Madeleine McCann Update: What Sunday's documentary will reveal about missing British girl

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On  May 3, 2007, 3-year-old Madeleine McCann was put to bed alongside her twin siblings by her parents in their vacation apartment in the coastal town of Praia da Luz, Portugal. Since that night, she has yet to be seen again.

Over the last 10 years, speculation has loomed as to what happened to the young British girl. Madeleine's parents, Kate and Gerry McCann, were even suspected in their own daughter's disappearance, however they were both cleared of "arguido" — or person being questioned — status in July 2008.

"It's hard to describe how utterly despairing it was for us to be named arguido and to subsequently be portrayed in the media as suspects in our own daughter's disappearance," the couple said in a statement to the Telegraph in 2008. "It's been equally devastating to witness the detrimental effect this status has had on the search for Madeleine."

Just this week, a nanny who worked for the resort the family stayed at broke her 10-year silence to lend her support to the McCanns and reaffirm their innocence.

The unnamed nanny told the Daily Mirror that Kate "was crying, but almost in a catatonic state, and Gerry was very distressed." She added that Gerry scrambled to look for his daughter around the resort and in the adjoining parking lot. "That's the one thing I really remember from him, looking under the cars. I can't forget that." She added that she believed there was absolutely no way the parents could be responsible, "A, timings, and B, where it was, their reactions, the whole thing. Not a chance."

Two retired detectives give updates in the McCann disappearance in 2009.  Oli Scarff/Getty Images

But the McCanns aren't the only theoretical suspects. Since 2007, as the Telegraph noted, every possible theory under the sun has been explored, including: "that Madeleine was abducted by a pedophile; that she was killed during a bungled burglary and her body dumped; that she was abducted by traffickers and sold to a childless couple; that she wandered out of the apartment and died in a tragic accident; and many more besides."

Unhappy with the Portuguese authorities' investigation, the McCanns instead turned to private investigators and police with Scotland Yard for help. In 2012, nearing the five-year anniversary of her disappearance, Detective Chief Inspector Andy Redwood with the Metropolitan police told the Guardian he believed Madeleine was abducted by a stranger, not by her parents, adding that there were 195 "investigative opportunities." But it's been five years since that statement, and the team has come up with little to no new evidence. Perhaps the sheer lack of facts in this case is what makes this coming Sunday Night special on Channel 7 about the young girl so intriguing.

"To some, the McCann's were tragic victims. To others, they were negligent parents – or even worse, cold-blooded killers," Channel 7 teased of the special. "This Sunday, Rahni Sadler speaks to the experts at the heart of the mystery; the lead investigator, the forensic scientist, the criminal profiler." Sunday's show may also reveal more detail on a new potential lead discovered by British police.

In March 2017, it was announced that funding would soon run out for the investigation. But in a last breath of hope, detectives said they had identified an individual they wanted to question. According to the New Zealand Herald, the person in question was allegedly near the area when Madeleine went missing. Per a report in the newspaper Correio da Manha, as translated by the New Zealand Herald: "This new suspect is believed to be Portuguese and was apparently seen near the Ocean Club, where Kate and Gerry McCann were staying with their children when Madeleine disappeared. British police are understood to be preparing to question this new suspect."

Due to this possible new evidence, the detectives leading the case were given an extra 85,000 pounds sterling — which is roughly $108,000 — to extend their investigation through September 2017.  

To date, NewsHub reported, 12 million pounds sterling — just over $15 million — has been spent on the investigation. Even with this extensive funding, the investigative team looking into Madeleine's disappearance was scaled down from 29 detectives to just four in December 2015. So far, not a single lead, sighting nor piece of evidence has resulted in any substantial breakthrough.