Fresh searches are under way in Portugal in the investigation into the disappearance of Madeleine McCann.
Police divers entered the water early on Tuesday at the Barragem do Arade reservoir, about 30 miles from Praia da Luz, where Madeleine went missing in 2007.
A rigid-hull inflatable boat was sent into the water with two officers on board.
Portuguese police confirmed on Monday that they are co-ordinating searches in the Algarve at the request of German police and in the presence of British officers.
Detective Chief Inspector Mark Cranwell said: “The Met continues to work with and support colleagues in Portugal and Germany, with their investigations into the disappearance of Madeleine McCann.
“Met officers will be in Portugal and I am grateful to the Polícia Judiciária and Bundeskriminalamt for allowing us to be present whilst their work is ongoing, so that we can inform Madeleine’s family of any developments.”
A brief statement from the prosecutor’s office in the German city of Braunschweig confirmed the search but did not reveal why it was taking place.
Braunschweig prosecutor Christian Wolters told reporters that investigators were acting on the basis of “certain tips” but would not give further details.
Four teams of officers from the Portuguese Policia Judiciaria are involved in the operation, along with at least 20 of their German counterparts, Portuguese news outlet SIC said.
Others were seen with rakes and metal rods preparing to search the ground.
It has been reported that the prime suspect in Madeleine’s disappearance, convicted sex offender Christian Brueckner, 45, spent time in the area between 2000 and 2017.
Brueckner, who has denied involvement in Madeleine’s disappearance, was first identified as a suspect by German investigators.
The Sun reported that the search was sparked after they discovered video and photos of Brueckner near the reservoir.
Brueckner is facing charges in Germany over a number of separate sex offences allegedly committed in Portugal during that time.
It is not the first time the reservoir has been searched.
The most recent search in Portugal in relation to her disappearance was in 2014, when British police were given permission to examine scrubland near where she vanished.
Earlier this month, Madeleine’s parents Kate and Gerry McCann posted a short statement on their Find Madeleine Campaign website to mark the anniversary of her disappearance.
“Still missing… still very much missed.
“The police investigation continues, and we await a breakthrough.”