Detectives investigating the disappearance of Madeleine McCann are awaiting test results on a key piece of forensic evidence which could provide the "decisive" breakthrough in the case.

Every detective in the Algarve remains on standby to launch new searches pending on the results, which are expected imminently.

Samples are still being analysed after a British sniffer dog found "specific clues in specific places" which have reportedly given police a new lead in the 15-week inquiry.

Chief Inspector Olegario Sousa, the spokesman for the Judicial Police, said yesterday: "The new line of inquiry can only go forward after these results."

Two British sniffer dogs - one specialising in detecting traces of blood and another which can pick up the scent of human remains - spent a week in the Algarve after being called in to help review evidence in the case.

They were used at the McCanns' apartment, where they detected specks of blood which have reportedly since been ruled out.

They also searched other apartments in the Ocean Club complex, surrounding roads, areas of the beach nearby and parts of the marina in Lagos, and various vehicles.

Samples are being analysed at the Forensic Science Services in Birmingham in a joint operation between Portuguese and British police forces.

Portuguese newspapers are describing it as the "decisive stage" in the inquiry.

Two of the detectives leading the inquiry, Guilhermino Encarnação, 59, the director of the Judicial Police for the Algarve and Goncal Amaral, arrived at a local headquarters in Portimao yesterday as the investigation gathered pace.

The Public Prosecutor's Office, which directs the police inquiry, signed a series of documents on Friday, ordering the Judicial Police in Faro to put detectives on standby and authorising search warrants at locations that may be linked to the disappearance of Madeleine 110 days ago.

The developments mark the first departure from investigations centred on Robert Murat, the only formal suspect in the case, who has been ruled out and will be cleared of his "arguido" status within weeks.

There has also been a shift in emphasis from police, who now believe that Madeleine is dead. It is unclear if they have come to that conclusion as a result of any forensic evidence.

A spokesperson for the McCann family said they had not been informed of any updates in the investigation.

Meanwhile it emerged yesterday that Mr McCann met the brother of executed hostage Ken Bigley this weekend.

Phil Bigley approached the McCanns while on holiday in Portugal with his family.

He spent several hours with Mr McCann talking about their experiences.

Ken Bigley was kidnapped and later beheaded while working as an engineer in Iraq in 2004.

Mr McCann wrote on his blog: "We had a British visitor who came to offer us a different type of support.

"He has been through an ordeal similar to ours involving one of his family.

"It was good to talk about our emotions, the pressures and different coping strategies that we use in an ongoing trauma, with someone who has experienced a tragic event like ours."