Scotland Yard has been given more money to probe an “important” new lead in the disappearance of Madeleine McCann.
The development is being taken so seriously that senior government officials have been briefed by the Metropolitan Police Service on its progress.
Detectives are following a tip that a gang of European traffickers snatched the tot after taking pictures of her.
It could end up proving that she is still alive, nearly 10 years after she vanished.
The search for Madeleine has been extended by months after Scotland Yard was given more cash.
But senior cops admit the investigation of the new lead is the “last throw of the dice” in their hunt.
A source said: “This is an important new line of inquiry which could provide an explanation on whether Madeleine was abducted and transported away.
“It raises hope that she could still be alive.”
Retired Yard detective Colin Sutton said the extra money for the last line of inquiry means “there must be something worthwhile.”
A focus of the inquiry is whether Madeleine, who vanished just days before her fourth birthday in May 2007, was abducted by traffickers.
One witness has claimed the youngster was photographed on the beach with her parents in the days leading up to her disappearance.
Madeleine was on holiday with her family in Praia da Luz, in Portugal’s Algarve.
The last-ditch move to discover her fate comes eight months after Met commissioner Sir Bernard Hogan-Howe predicted the force’s £12 million ($15.3 million) Operation Grange probe was coming to an end.
He had said that it was likely to conclude within a few months after a final matter was checked out.
Grange’s extension offers renewed hope for Madeleine’s parents, Kate and Gerry, both 48, from Rothley, Leicestershire.
The couple also believe their daughter, who would now be 13, could have been kidnapped and sold by traffickers.
They have researched human trafficking comprehensively since Madeleine vanished and Kate has met representatives from several charities that help victims.
Reports following Madeleine’s disappearance suggested she could have been taken to Belgium or Morocco in North Africa.
She vanished from her bed in a holiday apartment while her parents ate a tapas meal nearby with friends.
The source said: “There is specific information which is being investigated.
“The team is trying to confirm or disprove it and will exhaust every possible avenue of information, as they always promised Mr. and Mrs. McCann they would.’’
The source said: “The Home Office has agreed to continue funding the police work until it is completed.
“At present, funding is due to run out next April when it will be reviewed again.”
The child trafficking theory was first raised by private investigators working for the McCanns in late 2007.
They believed there could have been a gang of “spotters” working in the Portuguese resort.
There were reports of a man with binoculars looking at children on the beach and of men taking photos of kids.
The McCanns believe the pictures may have been shown to traffickers, who then selected Madeleine.
The theory was given further credence by Scotland Yard, which provided information about a Belgian pedophile ring to Portuguese authorities in March 2008.
The Met’s clubs and vice unit received a tip that the ring had placed an order for a “young girl” just three days before Madeleine went missing.
Leicestershire police, who at that point led the Operation Task effort to help find Madeleine, were also informed.
A friend of the McCanns said: “Trafficking into Belgium and North Africa has always formed a very strong part of the investigation.
“There is definitive hard evidence that this is happening and they have looked into the fact someone was targeting children and may well have been stealing to order.”
In 2011, police in Portugal smashed a trafficking ring snatching young women and underage girls in the Algarve and Aveiro, in the north of the country.
Anti-child trafficking charity ECPAT International said Portugal was “attractive to traffickers” because of the ease with which children can be driven across borders.
Police have carried out excavations in Praia da Luz looking for Madeleine’s remains.
But they have always thought there was a possibility she was taken further afield, possibly by traffickers, a predatory pedophile or someone who wanted to raise her as their child.
The Grange investigation was launched in May 2011.
It followed a personal plea from Kate to then-Prime Minister David Cameron after the Portuguese closed down their inquiry.
In October last year, the Met probe was dramatically scaled down.
The Home Office granted the inquiry another £95,000 ($121,000) in April to continue for a further six months.
Sources say that has now been matched with a similar sum.
A family source said: “Kate and Gerry will not comment on any part of Operation Grange.”
The Met Police also declined to comment.