Police grilling Christian Brueckner over missing Madeleine McCann are now waiting for the results of forensic tests carried out on his VW van.
The German paedophile, who was made an official suspect by Portuguese authorities on Thursday, has been quizzed for the first time about her disappearance.
And one UK child exploitation expert tonight said he believed it was only a matter of time before Brueckner was charged.
German detectives quizzed the 44-year-old in Oldenburg jail where he is serving time for rape, at the request of Portuguese prosecutors.
He was asked: “Where were you the night Madeleine McCann disappeared?” They also wanted to know if he had an alibi, adding: “If you weren’t by the apartment she disappeared from, where were you?”
Brueckner was handed a document informing him he was being made an arguido, a Portuguese legal term.
Sources close to the case said he answered none of the questions. His lawyer is thought to have been present during the key development.
Brueckner drove the VW van that is being examined while living on the Algarve, where Madeleine vanished on May 3, 2007, aged three from her family’s holiday apartment in the beach resort of Praia da Luz.
Former head of the Child Exploitation and Online Protection Centre, Jim Gamble – who worked on the investigation into the youngster’s disappearance – said the “breakthrough could mean everything or it could mean nothing”.
He added: “My gut feeling on it, from the moment the Germans began to release information two years ago, was that this was the best fit.
“You have proximity, you have opportunity, and you have a profile with regards to an offender that fits in a way that no others have. This is all positive. And I wouldn’t be surprised if charges did follow.”
Prosecutors in Germany had announced almost two years ago they believe Brueckner killed Maddie and they had “concrete evidence” she was dead. The new questions were prepared by prosecutors in the Algarve resort of Portimao.
Portugal’s Policia Judiciaria force, which has officers leading an ongoing review of the case from Porto, has yet to make an official comment.
But a source said today: “The PJ is committed to finding out what happened to Madeleine and in addition to the work we’re doing, we will continue to co-operate with British and German authorities.”
It is thought Brueckner has been made a suspect as there is a 15-year time limit for a murder charge in Portugal, which elapses next month.
It gives authorities there the ability to charge him further down the line by effectively “stopping the clock” on the time limitation. One Portuguese insider described the move as “potentially crucial”.
But he added: “It could also be the final throw of the dice. It’s a wait and see situation.”
Sources have said the legal grounds for making Brueckner an arguido include the fact he allegedly confessed to a pal he had snatched Madeleine and mobile phone records placed him in Praia da Luz the night she vanished. Madeleine’s parents Kate and Gerry, who were made arguidos in September 2007 before having the status lifted the following July, said they “welcome the news Portuguese authorities have declared a German man an ‘arguido’ in relation to the disappearance of our beloved Madeleine”.
The couple, of Rothley, Leics, added: “This reflects progress in the investigation, being conducted by the Portuguese, German and British authorities.
“Even though the possibility may be slim, we have not given up hope that Madeleine is still alive and we will be reunited with her.”
German prosecutor Hans Christian Wolters said today the investigation into Brueckner could run into next year.
The pervert is serving seven years for raping an American pensioner in 2005 in Praia da Luz.
He spent several years living on the Algarve and was jailed for nine months there for petrol theft.
Brueckner faces three separate sex crime charges including the rape of an Irish woman in 2004 in Portugal.
