In new developments in the search for Madeleine McCann, police were reportedly hunting for a camera which may hold key evidence.
Investigators are desperate to find the footage which they believe is that of Madeleine as well as, other victims who could have been attacked by the same man.
German investigators requested that Portuguese police spend three days searching the area of Arade dam and reservoir, which is about 30 miles from Praia Da Luz - where Madeleine was last seen alive in 2007 at the age of three.
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The reservoir was said to be well known to number one suspect and convicted German rapist Christian Brückner's, reports the Mirror.
Cops scoured the area after "certain tips" were given to German prosecutors about Brückner.
New developments have been made after information suggests officers were looking for a video camera that may contain crucial photographic evidence.
Reports say a criminal informer tipped off German prosecutors that items taken during a raid of Brückner's home were thrown into the reservoir.
Two key witnesses Manfred Seyferth and Helge Busching reportedly told German investigators they broke into Brückner's house while he was in jail - claiming to have found a gun and a video camera at the isolated house in Floral, where he lived, a few miles from the reservoir.
The pair have claimed that footage on the camera showed Brückner torturing and raping an American woman and a girl aged about 15.
However, Brückner says the men are seeking to set him up because a drug deal went wrong.
It had been reported that investigators previously found photos and a video of Brueckner at the reservoir, despite denying any involvement in the disappearance of Madeleine.
German authorities have not revealed what triggered the latest search operation, but the prosecutor for the city of Braunschweig, Christian Wolters, said they were acting on the basis of "certain tips".
It was the first search in nine years.
A number of evidence bags were seen being taken away from the scene and police said the search "resulted in the collection of some material that will be subject to the competent expertise", and that it would "be handed over to the German authorities".
Searches ended on Thursday with the reported discovery of a "relevant clue" as the area at the centre of the operation was revealed.
The focus was a 160 sq ft area used as an informal picnic spot by partygoers and drug users, where Brückner sold cannabis at parties held in the remote woodland.
Wolters told German public broadcaster NDR the new information had not come from the suspect and they did not have a confession or "any indication from the suspect of where it would make sense to search".
Madeleine was three when she vanished while on holiday with her family in Praia da Luz after they left her and her younger twin siblings asleep in their apartment while they went out to dinner with friends.
Brückner is currently in prison for raping a 72-year-old woman in the same area of the Algarve from where Madeleine went missing.
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