Police have told the parents of Madeleine McCann to abandon plans to leave Portugal amid new hopes of a breakthrough in the case.
Kate and Gerry McCann last week admitted for the first time they have considered a return to Britain, more than three months after their daughter disappeared in Praia da Luz.
Detectives now believe that abduction is no longer the main lead, and that Madeleine died in the apartment on the night she disappeared.
The source said: “There is nothing to stop the McCanns going home - they are not suspects - but we have told them that it is not good timing because the investigation has changed. It is active now in assuming that Madeleine is dead.”
Family friends of the McCanns said there were no “concrete plans” to leave Portugal and they had ongoing telephone discussions with police about their day-to-day and long term future plans.
The source said that the key focus is now the two-bedroom apartment in the Ocean Club, where the four-year-old disappeared on May 3.
"The answers to this case are all in the apartment,” he said.
The developments have been marked by a noticeable “political” shift in the handling of the investigation, with police now actively briefing and giving public interviews.
Alipio Ribeiro, the national director of the Policia Judiciaria - Portugal’s most senior police officer - announced that police now assume Madeleine is dead last week, and Olegario Sousa, a spokesman for the Policia Judiciara, yesterday gave a third interview in the past week.
The burst of activity has fuelled suggestions that the investigation is reaching a “decisive” stage.
Mr Sousa said that detectives have a “positive feeling” about the inquiry and that the picture of what happened to the four-year-old on the night she disappeared is becoming clearer.
He revealed it was four weeks ago that detectives decided Madeleine was probably dead - before British sniffer dogs were sent out to help the inquiry.
He said: “Before the searches by the English dogs, one of the tasks carried out in the investigation allowed us to see some consistency in this line of investigation. “The hypothesis has been on the table for some time, and is stronger than the others.”
Mr Sousa also revealed detectives believe more than one person was involved in what happened to Madeleine.
He said: “It’s natural that in a crime of this nature more than one person took part. This analysis is not based on anything concrete, but rather on logic.
“If it was committed by only one person, it would be even more difficult to resolve the case because he or she is the only person who knows what they did.”
One possible lead led to detectives being placed on standby to launch new searches over the weekend. But they are still believed to be awaiting for key forensic test results to be returned from Britain before launching an operation.
Mr Sousa also played down reports that a new suspect was about to be arrested in Britain, dismissing them as old speculation.
It referred to Dr Russell O’Brien, a friend of the McCanns, who has become the latest victim of a smear campaign in a Portuguese newspaper, which claimed he would be arrested yesterday in connection to the disappearance.
He hit back and told friends: “I will robustly defend my reputation. I have not been contacted by the Portuguese police and there has been no mention of any impending arrest or need to return to Portugal. The allegations made in Portuguese press are completely without foundation.”
Dr O’Brien was dining with the McCanns on the night Madeleine disappeared and spent part of the evening away from the table looking after his own daughter, who was sick.
It is understood he shared duties with his partner Jane Tanner.
Rachael Oldfield, another friend who was dining with them, said: “It is just ludicrous. He is a lovely bloke. This is a total smear.”
In an interview with a Spanish newspaper, Mr and Mrs McCann were asked if they had any suspicions of their friends. Mr McCann immediately and firmly said “no".
Mr McCann added: “We trust our friends.”
As well as dismissing the speculation, Mr Sousa defended the officers investigating the case.
Asked if his colleagues’ inexperience in missing children cases may have hindered the search, Mr Sousa replied: “I don’t believe so, but it will only be possible at the end of the investigation to analyse all the decisions taken, and to know if at any stage we did things wrong.”
Mr Sousa admitted that the case could be “sent to the archive” if the four-year-old is not found, all leads are exhausted and nobody is prosecuted over her disappearance.
But he added: “I believe and hope that this will not happen, because I have faith my colleagues will solve this mystery, which is a complicated case.”