British detectives are using ground-penetrating radar and sniffer dogs to search scrubland in the Portuguese resort where Madeleine McCann went missing from seven years ago.
Officers are thought to be looking for disturbed earth in the hilly area, which is being guarded day and night by armed local police with dogs.
Madeleine’s parents Kate and Gerry are not in Portugal but are being kept informed by Scotland Yard.
Their lawyer Isabel Duarte told The Sun: “It is my belief that police have some very good information to be carrying out ground searches.
“I believe there is data in the file which has led to this operation because, if not, the police wouldn’t be performing this very drastic task.
“Kate and Gerry have not been given information that Madeleine is dead and until this happens they have to believe she is still alive.
“But they think police will come up with some significant news. It is such a stressful time for them.
The officers, who were in Metropolitan Police uniform, searched the long grass on their hands and knees, accompanied by one of the two sniffer dogs as they scanned the rubbish-strewn ground.
A British police officer could be seen collecting soil samples from one flat area inside the cordon, which had been marked out with tape while small yellow flags could be seen poking out of the ground in places.
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Nearby forestry workers used strimmers to cut back swathes of undergrowth to aid the search.
A large yellow-and-white cordon was put in place ahead of the search of clues and a number of small tents have been erected inside the cordon, thought to be where officers are concentrating their efforts.
Around six Portuguese police vans could be seen on top of a large mound in the middle of the scrubland, which overlooks the sea.
A number of officers from both the UK and Portugal could also be seen in discussions on top of the slope, which is covered in small bushes.
The land, a few minutes' walk from the Ocean Club resort apartment where Madeleine was staying with her family, has been searched before.
Scotland Yard, which is carrying out its own investigation into what happened to the youngster, refused to comment on British officers being at the scene and said the force was "not prepared to give a running commentary" about the case.
TV crews and journalists from around the world were gathered at the cordon as the search - seen as one of the biggest developments in the investigation in recent years - takes place.
Two local officers on horseback also patrolled the scene, while another pair strolled around the cordon edge with German shepherd dogs.
Two small blue tents around 100 yards inside appeared empty, with officers appearing to concentrate their efforts on the other side of the mound, away from the public's gaze.