Detectives investigating the disappearance of Madeleine McCann will reportedly begin questioning 11 people on Tueday.
British police working on the hunt for the missing girl are thought to have arrived in the Algarve to take part in interviews with individuals who it is thought may have information relating to the case.
Police are expected to question two other British people and seven Portuguese citizens.
BBC correspondent Christian Fraser said the authorities would be looking for “inconsistencies” with any answers given seven years ago.
They will spend three days working on the case alongside their Portuguese counterparts, according to reports.
Scotland Yard has declined to comment, saying it will not provide a "running commentary" on the inquiry.
The delegation in Portugal is believed to include the incoming head of the British side of the investigation after it emerged last week that the officer who has led Operation Grange since it was launched in 2011 is to step down before Christmas.
Detective Chief Inspector Nicola Wall will officially replace Detective Chief Inspector Andy Redwood, who is to retire, on December 22.
Scotland Yard said a handover was currently taking place and Kate and Gerry McCann, Madeleine's parents, had been informed of the change.
British officers spent eight days searching three areas of land in the Algarve resort of Praia da Luz in June, close to where Madeleine disappeared more than seven years ago, but found no new evidence.
Madeleine, then aged three, disappeared from her holiday apartment on May 3 2007 as her parents dined at a nearby tapas restaurant with friends, and it became one of the most famous missing persons cases of all time.
Portuguese police closed down their investigation in 2008 but the Metropolitan Police launched their own operation three years later.