Portuguese authorities have reportedly been searching wells that are a 20-minute drive from where Madeleine McCann disappeared in 2007.
The wells are around 10 miles west of Praia da Luz where Madeleine, who was three-years-old at the time, vanished thirteen years ago.
Multiple investigators were at the scene with specialist diving equipment to examine the wells, with the largest thought to be more than 13 metres deep.
According to the Mirror, Madeleine’s parents Kate and Gerry McCann have not been told on what grounds authorities searched the wells.
It was also reported the search sites are near a beach where the main suspect's camper van was photographed in 2007.
The investigation into Madeleine’s disappearance was renewed in June after German authorities announced they were investigating a convicted German child sex offender, who is referred to as Christian B by local media in Germany due to strict rules on the naming of criminals and suspects.
According to the Portuguese state broadcaster RTP, detectives said they discovered "fundamental evidence" that he is responsible for the youngster's disappearance.
The suspect is known to have lived on the Algarve coast and his Portuguese mobile phone received a half-hour phone call in Praia da Luz around an hour before Madeleine went missing in May 2007.
He is in jail in Germany for drug dealing, and is appealing against a conviction for the 2005 rape of a 72-year-old woman, also at Praia da Luz.
He has not yet spoken to investigators, who say they are convinced that he has committed other sex attacks.
Thursday’s searches come after Madeleine's parents denied receiving a letter from German investigators stating “there is evidence or proof” their daughter is dead.
Mr and Mrs McCann said the claims caused “unnecessary anxiety to friends and family and once again disrupted our lives”.
The couple also said that they do not have a family spokesman, and are not actively paying any lawyers to represent them.
German prosecutor Hans Christian Wolters, who is leading the investigation into the main suspect in Madeleine’s disappearance, said that a letter had been written to the couple, but would not reveal what it said.
Mr Wolters said prosecutors have “concrete evidence”, but not “forensic evidence” that Madeleine was killed by the suspect and may “know more” than Scotland Yard, who are still treating the case as a missing person investigation.
The Metropolitan Police maintain their active investigation into Madeleine’s disappearance, Operation Grange, is a missing person inquiry as there is no “definitive evidence whether Madeleine is alive or dead”.
In the days after the renewed appeal, Scotland Yard said they received nearly 400 tips to their Operation Grange team.
Additional reporting by the Press Association.