A new dossier of mobile phone calls is believed to contain numbers that have yet to be identified - and officers hope they could provide vital new leads

Missing: Maddie

Detectives are examining mobile phone information they believe could hold the key to Madeleine McCann’s disappearance.

Portuguese authorities are thought to have provided Scotland Yard with a list of calls made in and around the Ocean Club in Praia de Luz between 9pm and 10pm on May 3 2007 – the night the three-year-old vanished.

The dossier is believed to contain phone numbers that have yet to be identified, and officers hope they could provide vital new leads.

Detectives hope to track down the registered owner of each phone, and check whether any are known sex offenders.

The information was sent to the Met in response to an “international letter of request” asking for assistance from foreign police forces in 31 countries.

The requests are believed to relate to unidentified mobile phone numbers and it is the first time they have been analysed in detail. The Met are preparing to send another letter of request soon, sources said.

Detectives and Crown Prosecution Service lawyers are believed to have prepared a string of ILORs but remain hopeful that a joint probe can be established, rendering them unnecessary.

If an arrangement cannot be reached then it is feared the British investigation could drag on for years and end up costing at least double the £5million already spent.

Portuguese police revealed in October that their investigation was being restarted as a result of new lines of inquiry emerging from their own internal review.

They had originally shelved their probe in 2008, the year after Madeleine vanished, but supported the British-run enquiry. i

Detective Chief Inspector Andy Redwood, the officer spearheading the probe, revealed in October that the records could hold the key.

He said the analysis was a “targeted attack on that data to see whether it can assist us”.

He added: “We’ve got a data set of phone traffic. Within that phone traffic, you can see we’ve got some of those numbers we can attribute to people, but a large number of them we can’t ...

"A lot of the focus is not necessarily to find a suspect, but also witnesses. We’re trying to understand who was there for a range of reasons.”

Portuguese police have always had the phone records but they have never been examined in such detail.

The Met is now examining 41 persons of interest, including 15 UK nationals.

A Met police spokesman said: “We are not giving a running commentary. However we will issue details of any new ILOR issued to the Portuguese authorities.”