An investigation by Australian TV show Sunday Night said a new key witness is being sought and that Maddie’s body was dumped in one of 600 wells in the Portuguese resort where she went missing 10 years ago.
While a senior professor also claimed Maddie could have been knocked down by a drink-driver after leaving the apartment to search for her parents.
The driver may have thrown her body down one of the wells – or disposed of it in mountain caves near to Praia da Luz.
And her corpse could still be there today.
Prof Dave Barclay said: “A drink driver would certainly have a motive to conceal a body.”
Maddie was three-years-old when she disappeared from her holiday apartment in Praia da Luz, Portugal, on 3 May 2007.
Madeleine McCann has now been missing for 10 years
Now nearly 10 years on, former Scotland Yard Det Chief Insp Colin Sutton has revealed a witness had likely interacted with the McCann family during their stay.
He told the TV show which aired today: “There is an employee, somebody who worked within the Ocean Villa complex who has some information or some knowledge that may be of assistance.”
Sutton added it is possible little Maddie’s remains could still be hidden in the resort.
“It’s just large enough and difficult enough terrain to search in that we could throw all the resources available for both police forces and search for years and still not be satisfied you’d actually done it properly,” he said.
Another theory suggests Madeleine’s remains were dumped in one of the hundreds of wells in the area.
Journalist Paul Luckman, of The Portugal News and first on the scene, believes there are up to 600 wells scattered throughout the area.
“A drink driver would certainly have a motive to conceal a body”
Prof Dave Barclay
“In five, 10 years time, somebody suddenly decides to clear the well and they will bring it back into operation… they would clean it out and bones would be found,” he said.
The documentary went on to show parents Kate and Gerry McCann’s heartbreak as she discovered Maddie was missing.
Kate said there “wasn’t a day for 18 months” where she “didn’t cry for an extended period of time”.
Kate McCann (L) and her husband Gerry McCann (R), parents of missing British youngster Madeleine McCann, leave the court house in Lisbon after delivering statements in their case against Portuguese police officer Goncalo Amaral on July 8, 2014
Gerry added “Kate would howl like a wolf”, while he was struggling to contain his emotion.
The documentary had claimed it had a huge new lead in the case.
A spokesman for the McCanns previously asked the documentary-makers to hand over any evidence to police.
They said: “If the Australian TV show contains any credible, fresh lines of inquiry they should, of course, have been given immediately to the police.”