Scotland Yard detectives are in the process of routing through thousands of six-year-old mobile phone records to find missing Madeleine McCann.
Phones belonging to people in the Portuguese village of Praia de Luz, during 2007, are being investigated by police.
There are still 41 potential suspects although no one has been arrested.
Madeleine disappeared days before her fourth birthday while her family were on holiday in the Algarve.
Detective Chief Inspector Andy Redwood, who is leading the inquiry, said officers were examining a "substantial amount of data".
"This is not just a general trawl," said Det Ch Insp Redwood. "It's a targeted attack on that data to see if it assists us to find out what happened to Madeleine McCann at that time.
"We can see what the phone is doing, but we can't see the text messages. It shows a timeline of the call data."
Scotland Yard launched an investigation into Madeleine's disappearance in July.
They spent two years reviewing the case.
It is understood CCTV footage is being combed as part of Operation Grange.