SEARCH teams are expected to start excavating a number of sites in Portugal as part of the investigation into the disappearance of Madeleine McCann.

Portuguese authorities are understood to have given permission for the search of several sites in Praia da Luz, where Madeleine went missing in 2007, aged just three. The move comes just after the seventh anniversary of her disappearance on May 3 2007, part-way through a family holiday.

The request to search a number of sites is thought to be among a series of requests made by British detectives.

The excavations, which are expected to be conducted by forensic experts, are not thought to necessarily be in connection with a search for the youngster's body or remains.

Detectives from Scotland Yard are expected to be in Portugal for the searches, but it is not thought that Madeleine's parents Kate and Gerry will return to Praia da Luz.

Scotland Yard have refused to comment on the reports.

The McCanns' spokesman Clarence Mitchell said: "As always, we simply will not comment on operational details of Operation Grange, that is a matter for the Met Police. Kate and Gerry are being kept fully informed."

At the weekend, Mr and Mrs McCann thanked the public for their support at a prayer service on the seventh anniversary of her disappearance.

The couple were joined by around 100 well-wishers, friends and relatives for a low-key open-air service in the centre of Rothley, Leicestershire, which saw candles being lit for all children around the world who have been taken away from their parents.

Mr McCann, who is from Glasgow, expressed his family's gratitude that the Metropolitan Police team investigating Madeleine's disappearance was now moving on to a "very active" phase in their investigation, saying: "They are chipping away and obviously there is new evidence so we are going to continue to hope that we will get a happy outcome."

In a message posted at the weekend on the official website dedicated to finding Madeleine, Mrs McCann said: "Our situation seems as unbelievable as it did that very first night without Madeleine.

"We are hugely grateful to the general public for continuing to support the investigation, especially those who have found the courage to come forward with information despite difficult circumstances.

"We are grateful beyond words for the continued and unwavering commitment, help and love from all our faithful supporters."

Earlier, Mrs McCann disclosed that she privately returns to the Portuguese resort where her daughter disappeared to "walk those streets" and "look for answers", as she backed a revamped alert system triggered when missing children are kidnapped or their lives are at risk — known as Child Rescue Alerts.