Madeleine vanished in the Portuguese resort of Praia da Luz in 2007. She and her siblings had been left sleeping in a holiday apartment while her parents, Kate and Gerry, went to a nearby restaurant.
Madeleine’s disappearance has become one of the highest-profile unsolved missing person cases in the world.
German prosecutors have pointed to evidence – including mobile phone data – indicating Brückner may have been in the area when she vanished, and have consistently insisted that they think he is responsible.
However, they have not found strong enough evidence to bring charges.
Brückner, who spent many years in the Algarve, was a drifter, a petty criminal and a convicted sex offender. He has several previous convictions, including for sexually abusing children in 1994 and 2016.
Portuguese and German police conducted a fresh search between where the McCanns had been staying and addresses linked to Brückner in June this year, but this yielded no breakthroughs.