Madeleine McCann police are to question a number of suspects over her disappearance today (Tuesday).
Three Portuguese nationals and one Russian man will be interviewed in the Algarve region.
According to the BBC, the questioning follows a formal request by British police, who will sit in on the interview, but only Portuguese officers will ask questions.
The Russian suspect lived in Praia da Luz when Madeleine disappeared.
He was previously questioned by police during the first phase of the investigation by Portuguese police after Madeleine went missing in 2007, although he was never made a suspect.
The suspects are attending 'of their own free will' and will be made 'arguidos' - people of interest - after they meet police.
Eight witnesses are also due to be questioned at a police station in Faro.
Earlier in June, Portuguese and British police searched three sites in the Praia da Luz resort, but found no evidence relating to the case.
Scotland Yard said at the time that 'more activity' had been agreed with Portuguese police and the searches were the 'first phase' of a major investigation.
The searches were the most significant in the local area since Madeleine went missing seven years ago.
Her parents, Kate and Gerry, had been at a restaurant near their apartment when the three-year-old went missing.
The developments come after the Met launched Operation Grange - a fresh investigation into Madeleine's disappearance - last July.