Portuguese police are now working on the assumption that Madeleine McCann was abducted “to order” by an international paedophile network, after narrowing the focus of their six-day investigation.

Detectives have now discarded a range of other possibilities, including the theory that the British toddler could have walked out of her Algarve hotel room by herself or was kidnapped for adoption, Portuguese newspapers have reported.

“Everything points to a kidnapping,” a person close to the investigation told Correio da Manhã, adding that police were now exclusively investigating the possibility that she had been captured by a child abuse network. Police sources quoted anonymously by several other local newspapers said much the same thing.

Citing local laws, Portuguese police have refused to speak publicly about the state of their investigation. But recent moves have pointed to a renewed focus on international paedophile networks.

British officers specialising in child abduction cases have flown out to the Algarve. One of them, Detective Superintendent Graham Hill, is a veteran of missing child investigations and was one of the senior detectives in the hunt for 13-year old Milly Dowler, who vanished in March 2002. Her body was found in September that year, left in countryside in Hampshire. No one has ever been charged with the murder.

Mr Hill, who has been working for the Britain’s Child Exploitation and Online Protection Centre, was also a senior investigator in the hunt for Antoni Imiela, the serial rapist jailed in 2004 for attacks including five in Surrey. British detectives have also handed their Portuguese counterparts a list of people on the UK’s sex offenders register who have travelled recently to the country.

The growing certainty of investigators that three-year-old Madeleine was taken by child abusers will do nothing to console her distraught parents.

It would not be the first time that a child taken from Portugal has ended up in the grip of a paedophile ring. In 1998, an 11-year-old boy called Rui Pedro Mendonça vanished while walking home from school in the northern Portuguese town Lousada. A month later, hopes were raised when he was sighted with a middle-aged man in Disneyland in Paris. Then three years later, his mother’s worst fears were realised.

Horrific images of Rui Pedro being sexually abused were reportedly uncovered during an international police operation that cracked a global paedophile network. More than 200 paedophiles in 13 countries had exchanged more than 750,000 images of children through a private internet club called Wonderland.

Analysis showed that 1,236 children had been subjected to abuse that officers described as “unimaginable”. Some were babies, raped by their abusers. Others were sexually abused live, to order, online. Officers described weeping as they catalogued the pictures and being haunted for years afterwards.

The Portuguese boy’s mother, Filomena Teixera, flew to Switzerland to view the pictures and was apparently able to identify her son. But he has never been found. The trail has gone cold and investigators fear that may have been murdered to cover up the abuse. Now the disappearance of Madeleine has brought those agonising memories flooding back.

“When I saw the news about the disappearance of the English girl, I was terrified,” Ms Teixera told the 24 Horas newspaper. “I immediately thought of my son, even though the cases are different. And I thought of Madeleine’s parents, the anguish they are suffering.”

Ms Teixera said she has had psychiatric treatment for 8 hours a day for the past four years, since her father died. She still refuses to believe that her son, who would now be 20 years old, could have died.

“When I stop believing he is alive, I lose all my strength,” she said. “My brain doesn’t allow me to think the he is dead.”

Six other children are listed as having disappeared in Portugal. Not all are suspected of having been snatched by paedophiles, but one case in particular has drawn attention for its startling similarities. Rui Pereira was 13 years old when he vanished in 1999 -- just a few months after Rui Pedro -- from the northern town of Famalicão. There was later a reported sighting of the boy in Switzerland, in the company of two Italians.

His mother, Laurinda Meira, also continues to believe he is alive. “He must be tall,” she said two months ago, when he should have been celebrating his 22nd birthday. “I would like to open the door one day and find him there.”

All his clothes and possessions remain in the exactly the same place as they were when he vanished from their lives. “I am sure that he is alive, but not totally well” she told Portuguese daily, Journal de Notícias. “He could be into drugs, or prostitution or as a slave, we just don’t know.”

Portuguese police travelled to Switzerland in 2003 to check through database of paedophile images, but they have so far drawn a blank. The family has strongly criticised the Portuguese authorities, saying that the police did little to find their so. Supporters also mounted street protests when the courts tried to close the case.

Child protection campaigners have alleged that a culture of corruption and complacency in Portugal is allowing such kidnappings to continue unabated. The founder of the Switzerland-based group Innocence in Danger has said she had tried to set up an office in Portugal but it gave up because of the reluctance of the authorities.

Homayra Sellier said after Madeleine's dissappearance last week that Portugal is a country in which “the corruption has gone so high that there's nothing we can do”.

“The fact that the girl (Madeleine) was kidnapped from her bed shows how bad things are.”

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