Seven Portuguese officers entered the house at 7am yesterday and remained inside until the early afternoon as they continued to attempt to build a case against official suspects Kate and Gerry McCann.

Amongst them was Chief Inspector Tavares Almeida, the officer who interviewed Mrs McCann, and who recently asked to be taken off the case on unpaid leave.

Portuguese police are convinced that the holiday apartment in Praia da Luz "holds the key" to solving the case but it is not clear if they were following a specific lead.

It is understood that there were also new searches at the beach. DNA samples from the flat and the McCann's hire car, which were collected in late July by British police, are still being processed every week.

It emerged that lawyers acting for the parents have hired their own forensic experts to refute the DNA evidence allegedly linking them to the four-year-old's disappearance.

It is believed they had already "gone over" the Renault Scenic Mr and Mrs McCann hired 25 days after she went missing - in which it is alleged a complete DNA match with Madeleine was found.

The couple insist that all the allegations against them can be explained innocently and have gone "on the front foot" in putting together a defence case to clear them of their "arguido" status.

The McCanns' law firm Kingsley Napley, one of the leading criminal law firms in the country, is understood to have brought in their own experts to brief them on the feasibility of the alleged evidence being tested at the Forensic Science laboratory in Birmingham.

Mr and Mrs McCann are hoping that the appointment of a new police chief in the case will help them to shift the focus away from them and back to the hunt for Madeleine.

Paulo Rebelo, the national deputy director of the Policia Judiciaria, has been drafted in to replace the former head Goncalo Amaral, who was sacked after he accused British police of being manipulated by the McCanns.

It is believed Mr Rebelo may have been one of the officers at the Praia da Luz flat being shown the scene.

Although he has no previous experience of child abductions, he has played a part in some of the country's most high-profile cases, including one into the sexual abuse of children at an orphanage. Colleagues say he is discreet, articulate and approachable.

Clarence Mitchell, a spokesman for the couple, said: "Kate and Gerry hope that Mr Rebelo will now work to eliminate them from the inquiry as suspects and will then be in a position to refocus his team into the search for Madeleine.

"Clearly we hope that a new head of the inquiry will work to ensure the unsubstantiated and unfounded allegations surrounding the case will now end."

Mr Mitchell said the parents were unable to move on or grieve for Madeleine until they knew for definite what had happened to her.

"They need that knowledge whether Madeleine is alive or dead - let's face it, she might be," he said in an interview with GMTV.

"They need to know, before they can move on, before they can deal with that."

The incessant speculation continued, however, including one report claiming that the McCanns and the three couples they were on holiday with left of their children sleeping in the McCann's apartment while they dined in a nearby tapas restaurant.

Portuguese newspaper 24 Horas reported, quoting a senior PJ officer as claiming: "It's not just the evidence gathered which point to the fact of there being more children in the apartment, there is also the evidence duly backed up after interrogation upon the rest of the people who were in the Ocean Club."

None of the McCann's friends were available for comment but Mr Mitchell dismissed the claims as "utter rubbish", saying only Madeleine and her two-year-old twin siblings Sean and Amelie slept there.

"If you put seven children together, you're going to have a far harder time getting them to sleep than three," he said