Madeleine McCann has been missing since May 2007

 Spanish private detectives claim they have handed Scotland Yard up to eight "very important leads" in the search for missing girl Madeleine McCann.

Four Metropolitan Police officers held talks with Barcelona firm Metodo 3, which investigated her disappearance on behalf of the family, sources said.

Officers travelled to Spain yesterday to pick up around 30 boxes of documents, investigator Francisco Marco Fernandez told Spanish TV.

Mr Fernandez, who was hired by parents Kate and Gerry for six months, told the Ana Rosa Programme he provided police "with all the documents and information we have collated worldwide about Madeleine's disappearance"

"I think there are six, seven or eight very important leads in there," he added.

A Scotland Yard spokesman refused to confirm the meeting took place. "We will not be providing a running commentary," he added

Parents Kate and Gerry McCann (Pic: DM)

Family spokesman Clarence Mitchell added: "Kate and Gerry will simply not be commenting whilst the Metropolitan Police review of Madeleine's case is under way.

"They remain pleased that the Met team is continuing its work and that progress is being made."

It is the second time officers are understood to have visited the Spanish city.

A team also spent three days with Spanish colleagues in Barcelona last month discussing the girl's disappearance across the border in Portugal.

The Metropolitan Police force has said there would be no limits in its re-examination of the search.

Madeleine was nearly four when she went missing from her family's holiday flat in Praia da Luz in the Algarve on May 3 2007 as her parents dined with friends nearby

The hotel in Algarve, Portgugal where Madeleine McCann went missing (Pic: PA)

Police have also travelled to Portugal three times in connection with the fresh review. A total of 30 people are now working on the force's Operation Grange.

The review prompted criticism when it was launched in May, with politicians expressing concerns that it would divert resources from other crime victims.

It was sparked after a request from Home Secretary Theresa May supported by Prime Minister David Cameron.

Portuguese detectives, helped by officers from Leicestershire Police, carried out a massive investigation into Madeleine's disappearance.

But the official inquiry was formally shelved in July 2008 and since then no police force has been actively looking for the missing child.