Police have not named the suspect in the disappearance of Madeleine McCann, but he has been partially identified in media reports as Christian Brueckner.
He is a German national aged 43. At the time Madeleine vanished on May 3, 2007 in Praia da Luz, Portugal, he was 30 years old and may have looked between 25 and his early 30s.
Christian Hoppe from Germany's Federal Criminal Police Office (BKA) told the country's ZDF television channel that he is currently serving a prison sentence for a sex crime and has two previous convictions for "sexual contact with girls".
German newspaper Braunschweiger Zeitung reported he is serving a seven-year prison sentence for the rape of a 72-year-old US woman in Portugal in 2005.
German magazine Der Spiegel reported he was extradited from Portugal in 2017 and initially convicted of drug trafficking.
He is known to have frequented the Praia da Luz area between 1995 and 2007, with some short spells in Germany.