Madeleine McCann's parents have hit out at claims their daughter woke up and wandered out of their holiday apartment before she went missing 11 years ago.
Police investigations by British and Portuguese detectives are believed to be re-visiting the theory the three-year-old left their Algarve apartment of her own accord before she disappeared.
But Kate and Gerry McCann have slammed the idea, insisting she was kidnapped by someone while they were on holiday in Praia da Luz in May 2007.
A family source said: "Kate and Gerry have always maintained that their daughter was abducted and simply didn't get up and wander off to her fate.
"There were heavy shutters which would have been impossible for a small child to open."
Claims Scotland Yard are looking into the possibility Maddie could have left the family villa, where she and her younger twin siblings had been left sleeping alone, come after it was revealed that UK detectives have told the McCanns' they are pursuing two vital new leads - not one final line of inquiry.
Mrs McCann spoke about the shutters in a TV interview with American chat show host Oprah Winfrey to mark the second anniversary of her daughter's disappearance.
Re-living the horror she felt as she searched the apartment and noticed the shutters open, she said: "That was when I knew that someone had taken her. It was obvious because a child could not open those shutters."
The British and Portuguese efforts to find out what happened to the toddler are being carried out separately - but the two are believed to have met to discuss the theory she woke up and wandered off.
A spokesman for Portugal's Attorney General's Office refused to comment, but a well-placed source said: "The heads of the two police investigations are corresponding with each other directly and have combined their efforts without resorting to rogatory letters like before.
"A meeting took place recently at the HQ of the General Attorney's Office in Portugal, which was attended by the prosecutor from Portimao who is in charge of the Portuguese inquiry.
"One of the lines of investigation that continues to be pursued is that the child could have walked out of the holiday flat herself."
Rogatory letters are ones sent to a foreign court to help in the pursuit of justice.
The last of the six sent to the Portuguese police by their British counterparts was answered on October 25 2016, but none have been sent since.
Another well-informed insider added: "Despite the fact there are two investigations and two different teams, the relationship between both is very healthy and well-informed and benefits from shared intelligence."
Hinting both forces may have gone cold on the idea the youngster had been the victim of a botched burglary or a paedophile who had forced entry to snatch her, the insider said: "The theory that Madeleine left the flat of her own accord to go looking for her parents is not something that hasn't been discussed before.
"But the Portuguese process tends to value lines of investigation that are put forward.
"Until we know for sure what happened though, no scenario is likely to be ruled out."
A third source, referring to the absence of new rogatory letters, said: "The pattern of direct cooperation that now exists means formal requests for international cooperation are not necessary.
"The Portuguese inquiry is still open, meaning that any new work can be executed as part of that investigation without the needs for rogatory letters."
The theory Madeline may have lost her way in the dark and taken a wrong turn as she went looking for her parents was one of the early hypotheses put forward to explain her disappearance.
It has also been suggested a panicking drink-driver might have run her over and sped off with her body before hiding it in the countryside.
Portuguese police have made no secret of their rejection of the theory championed by a British detective about Madeleine being kidnapped by thieves during a bungled burglary.
In July 2014 four Portuguese men faced a barrage of more than 250 questions while being quizzed as arguidos or formal suspects in interviews on the Algarve conducted at Scotland Yard's request.
They were questioned as part of the theory Madeleine may have been killed during a botched break-in and her body buried on waste ground nearby.
More recently it has been suggested officers are keen to identify a woman in purple seen hanging round the holiday flat around the time Madeleine went missing.
The Home Office announced last week it would grant an extra £150,000 (NZ) $288,000to Operation Grange, which has cost the taxpayer £11.75million (NZ$22m) so far, to keep the investigation going until spring next year.
It is understood police recently told her parents during a meeting at their Leicestershire home that they were 'hopeful' of a result and were focusing on 'two specific and active' lines of inquiry, not just one as was initially thought.
Scotland Yard has refused to go public with details on what they are looking at.