Madeleine McCann mystery: Police to dig in Portugal wasteland

(CNN) -- British police investigating the 2007 disappearance of Madeleine McCann will begin digging this week in an area of wasteland close to where she went missing in Portugal, sources close to the investigation have told CNN.

Media have gathered outside a cordoned-off area of the beach resort town of Praia da Luz, in Portugal's Algarve region, but it is unclear when digging will begin.

Madeleine was a few weeks shy of her fourth birthday when she disappeared from her family's holiday apartment on May 3, 2007.

Her parents had left Madeleine and her younger twin siblings asleep while they went for dinner with friends at a tapas restaurant nearby. Her mother raised the alarm when she checked on the children about 10 p.m. and discovered her daughter missing.

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CNN understands that London's Metropolitan Police will be in charge of the new digging operation in abandoned terrain close to where Madeleine disappeared. A large investigation team is expected to use dogs and radar in the search and dig a number of holes, sources said.

Portuguese police searched the area soon after Madeleine's disappearance, and it is understood they will intervene only if a body is found.

Sources told CNN that British police were working on the assumption that Madeleine was dead, while their Portuguese counterparts were working on the assumption that she was still alive and had been taken out of Portugal by a non-Portuguese national who had been in the country for a short time.

Scotland Yard -- as London's Metropolitan Police are known -- has not commented on the latest development, other than to confirm that British officers would be in Praia da Luz this week.

On May 22, its head of specialist crime and operations, Assistant Commissioner Mark Rowley, told media there would be 'specific police activity' in Portugal in the coming weeks, relating to Madeleine's disappearance.

'It should not be assumed that this substantial upcoming phase of work in Portugal will immediately lead us to the answers that will explain what has happened,' he warned. 'What you will see is normal police activity you would expect in any such major investigation.'

Rowley said the senior investigator in the case, Detective Chief Inspector Andy Redwood, and his team would be traveling to Portugal but would not be commenting on the investigation.

He reiterated that Portuguese police had advised Metropolitan Police that they did not brief media on current investigations.

'They clearly stated that if the MPS (Metropolitan Police Service) provide any briefings or information on the work they are undertaking on our behalf, or if reporters cause any disruption to their work in Portugal, activity will cease until that problem dissipates,' Rowley said.

'We have made it clear to colleagues in Portugal that we will not be giving operational updates,' he said. 'If media interfere with police work, that work will stop.'

In July 2013, Scotland Yard reopened its investigation into Madeleine's disappearance after a two-year review of the original probe. Portuguese police reopened their investigation last October.

At the time, the Metropolitan Police said the two police forces' investigations would run in parallel.

Madeleine's parents -- Kate and Gerry McCann -- launched a massive publicity campaign to find their daughter after she went missing and say they continue to believe she is still alive.