Phone data may yield new lead in Madeleine inquiry British police say an analysis of mobile phone data from thousands of people who were in a Portuguese resort when British girl Madeleine McCann disappeared in 2007 could provide a new lead. An appeal based on "substantive" new information will be broadcast on a BBC TV program on October 14. Police are analysing data from phones belonging to people who were in Praia da Luz when Madeleine vanished in May 2007 and they are investigating 41 potential suspects, although no arrests have been made. "The mobile phone data is a substantial amount of data," said Detective Chief Inspector Andy Redwood, who is leading the inquiry, but he added that much of it was "unattributable." Asked if the information could provide a breakthrough in the investigation, Chief Inspector Redwood said: "It could do. Putting this with layers and layers of other information; we are carrying out a targeted attack on the information. It is like pulling back the layers of an onion," he said on Friday. Chief Inspector Redwood admitted officers had so far been unable to match a "large number" of mobile numbers to the users of the phones. He said the task was complicated by the fact that many of the phones operated on a pay-as-you-go basis. Madeleine's parents, Gerry and Kate McCann, have never abandoned their campaign to find Madeleine, who was just about to turn four when she disappeared as she slept in the family's holiday apartment on May 3, 2007. Her parents were dining with friends in a nearby restaurant at the time. Portuguese authorities closed their investigation in 2008. But London's Metropolitan Police spent two years reviewing the evidence and announced in July that they were launching an investigation into Madeleine's disappearance. British police are working with detectives from Faro, in the Algarve. Detectives said the number of "persons of interest" was 41, of whom 15 were British nationals, but no arrests had been made.