COPS are searching a remote reservoir and dam that Madeleine McCann suspect Christian B dubbed his "little paradise".
The desolate site is just 45 minutes from the Ocean Club apartment in Praia da Luz, Portugal - where the three-year-old girl vanished on a family holiday in 2007.
Pictures on Monday showed police tents being erected and officers scouring the shoreline at the Barragem do Arade reservoir near Silves as they prepare for the major search on Tuesday.
The specific evidence that sparked the renewed hunt remains unknown.
Here, we have broken down some of the clues that link Christian B - or his alleged victim - to the area.
1. Christian B camped and slept at the reservoir
Christian B is understood to have often visited the site - and used it as a "base".
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In his camper van, he is reported to have frequently stayed overnight and dubbed it his “little paradise”.
Christian B has reportedly been “seen there often” and would sometimes spend the night in the barren area.
A source also told The Sun that the sex offender would use the area as a base.
Portuguese broadcaster SIC reported German police sought permission to search the dam in an official judicial request to Portugal after concluding it was an “area of interest.”
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It said: “Investigators know suspect Christian B used to come to this dam regularly.
“He would call it his little paradise and would often spend the night here. He was seen here often.
“The German authorities considered this reservoir to be an area of interest and ended up sending an International letter of request or letter rogatory.”
It is understood the new hunt is a German-led operation which was being coordinated with the help of Portuguese police.
German police have had a long-running probe into Christian B - and despite slow progress just last month vowed "nothing had changed".
Christian B's lawyers have been defiant and have long insisted his innocence.
A source told The Sun: “British authorities will come too to supervise and the Germans may join the search. The operation is expected to last two days- maybe more.
“We are also hearing criminal science experts will join.
“Most of it will take place on land but also part on the dam water, which is currently very shallow owing to a drought.”
The probe is expected to include divers exploring the murky depths of the reservoir behind the dam, while cops are expected to dig up the woods by the water.
Local reports are claiming around “80 per cent” of the searches will be land searches and the rest underwater ones.
2. The suspect lived in a villa only 12 miles from the site
Christian B is alleged to have lived very close to the site that he visited “often” at one point.
A source told The Sun that “[Christian B] moved around that area. He had a house 12miles from the place.”
Arade Dam is also located in-between where Christian B would park his grotty camper van in Praia da Luz and the creepy isolated villa in which he would stay in Foral.
The site is only a 40 minute drive from his abandoned Portugal residence.
3. A possible sighting of Madeleine in the area
The site of the current search is only a short drive from Silves where a trucker reported a sighting to police two days after Madeleine went missing.
The man alleged that he saw a woman hand over a child that looked like the missing toddler to a mystery man – a piece of possible evidence that has be combed over thoroughly by police in the past.
4. The underworld tip-off that claimed Madeleine was in the lake
The same reservoir was searched twice in February and March 2008 by divers hired by a Portuguese lawyer.
Marcos Aragao Correia organised the privately-funded operation after he claimed to have received an “underworld” tip.
The lawyer alleged that his contacts told him Madeleine had been murdered and her body thrown into the reservoir within 48 hours of her disappearance.
In 2008, Marcos said: “They told me she was thrown into a deserted lake with murky waters. I’m convinced this is the place.
“My sources told me Madeleine was thrown into a deserted lake with murky waters, a beach and lots of trees.
“I believe this would have been the best place for someone to have dumped the body, based on my investigations.”
He explained that the police ignored his tip-off, adding: “I was able to identify the site on December 10 and immediately informed police, who did nothing.
“I got tired of waiting for them to act on my information, so I decided to act.”
5. Clues found during a search of the lake in 2008
The search dredged up several suspicious items from the reservoir which is 150ft deep in places, but none that were used in the investigation.
Divers uncovered a 17ft cord, some plastic tape and a single white cotton sock.
Two bags containing small bones were found during the second search.
Portuguese police were alerted following the discovery but subsequently ruled out the possibility the bones were human because of their size.
Madeleine’s parents Gerry and Kate McCann had previously dismissed Mr Correia as a self-publicist and said there was no evidence suggesting any link between their daughter and the reservoir.
It is not known to have been searched since March 2008 as part of the ongoing investigation into her disappearance.
Earlier this month Kate and Gerry posted a poignant tribute to mark their daughter’s 20th birthday, telling her: “We love you and we’re waiting for you. We’re never going to give up.”
They added: “Happy Birthday Madeleine. Still missing. Still very much missed. Still looking. For as long as it takes.”
The message on the official Find Maddie Campaign Facebook page accompanied a cherished last photo of her as a three-year-old, beaming in a pink sunhat and clutching tennis balls.
Kate and Gerry are expected to be kept informed of any developments as a result of the new search through Scotland Yard liaison officers.
German prosecutor Hans Christian Wolters has consistently said he is convinced Madeleine is dead and the caged paedophile, 45, has been named as the sole suspect.
The deviant, currently serving time for the September 2005 rape of a 72-year-old American in the resort where Madeleine vanished, has not faced any formal accusation over the youngster’s disappearance.
Last April he was made an official suspect over Madeleine’s disappearance.
In the autumn, he was charged in Germany with several sex crimes in the Algarve against women and children,
These included the rape of an Irish holiday rep in 2004 and the sexual abuse of a female child on a beach near Praia da Luz in 2007.
His lawyer revealed in April those charges had been dropped against him in a bombshell development after successfully arguing prosecutors had no jurisdiction over him in Braunschweig where the Madeleine case was being brought.
Braunschweig prosecutor Mr Wolters has insisted they are still in control of the Madeleine McCann investigation.
In July 2020 Portuguese police and firefighters searched three wells for Madeleine’s body but failed to find any trace of her.
The abandoned wells are a 15 minute drive from a cottage rented on the outskirts of Praia da Luz, on a narrow road leading down to a beach where the paedophile used to park his VW camper van.
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The Scotland Yard digs nearly nine years ago in Praia da Luz were linked to the leading UK police theory at the time Madeleine died during a break-in and burglars dumped her body nearby.
The searches failed to find any trace of the missing youngster.