Portuguese police will on Tuesday search a reservoir inland from where British three-year-old Madeleine McCann disappeared in 2007, authorities said, in the first formal development in the case in Portugal in several years.
A fire brigade spokesperson said police were preparing to start searches on Tuesday at a dam in the southern region of Algarve about 50 km (31.07 miles) inland from a beach resort where Madeleine went missing from a rented apartment while on a family holiday.
Police erected two tents beside the dam on Monday, Reuters TV footage showed.
A source familiar with the investigation told Reuters the operation in Silves municipality was being carried out at the request of German authorities, who last year formally identified German man Christian Brueckner as an official suspect in the disappearance of McCann.
German officials had no immediate comment.
Portugal's investigative Judicial Police in charge of the operation declined to comment.
A separate source familiar with the investigation was not optimistic about the chances of a breakthrough in the long-running case, adding: "It will come to nothing."
Is anyone held on charges of her disappearance?
Brueckner, a convicted child abuser and drug dealer, is behind bars in Germany for raping a 72-year-old woman in the same area of the Algarve from where Madeleine went missing.
German police said in June 2020 that Madeleine was assumed dead and that Brueckner was likely responsible for it. Brueckner has denied any involvement and has not been charged with any crime related to it.
A German court last month threw out additional charges against him related to other Portuguese child rape and sexual assault cases that meant the German prosecutors investigating the disappearance of "Maddie" no longer had jurisdiction to investigate it.
Maddie's parents Kate and Gerry McCann were questioned by Portuguese police as formal suspects in 2007, but police dropped their investigation the following year, citing a lack of evidence, and cleared them of any involvement.
The parents have since campaigned to draw attention to their daughter's disappearance, and British public figures from business tycoons to authors and soccer stars have made appeals for information.