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The Algarve site was close to the home of Nicole Fehlinger, Brueckner's ex, and is said to have never been searched before, according to her father Dieter.
Set over more than 5,000 square metres, the compound is said to have been guarded by four 'aggressive' dogs.
Dieter also claims that as the area was 'completely overgrown', no one would have been able to get in or out other than Nicole and 'perhaps Brueckner'.
He has now told investigators about the land, which is reportedly close to the house where Nicole lived, 38 miles from Praia da Luz.
The Mirror reports that Dieter went to speak to the German equivalent of the FBI for a second time, adding that prosecutors have confirmed Dieter gave a lengthy interview, and they are now investigating the lead.
Speaking to the outlet, Dieter said: "No one knows that my daughter not only had the private residence in Portugal at her disposal but also a separate compound.
"No one has ever searched there or the property has never turned up in connection with Maddie, Brueckner or Nicole.
"It's an overgrown property of over 5,000 square metres. It was a secure area, enclosed with fencing and four aggressive Kangal dogs were there day and night.
"The area is completely overgrown, not visible. No one could get in or out, only my daughter and perhaps Brueckner with her."
German police are investigating Brueckner, 44, after naming him as the prime suspect in the disappearance of McCann last year.
Madeleine McCann went missing from her apartment in 2007 while on holiday in Portugal, days before her fourth birthday.
Her parents Kate and Gerry had gone out for tapas with friends while Madeleine and siblings were in bed. When they got back, she had disappeared, and was never seen again.
Investigators had feared Brueckner moved Maddie to his homeland in Germany after abducting her.
However, prosecutor Hans Christian Wolters now says police believe Maddie - who would now have been 18 years old - was killed in Portugal.
Bruecker is currently serving a seven-year sentence for raping an elderly American woman at her home in Praia da Luz.
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