Madeleine McCann died from an overdose of sleeping tablets, reports in a French newspaper claimed yesterday.

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Guilhem Battut, an investigative reporter for the French tabloid France Soir, said Portuguese police had given prosecutors a file detailing how they thought Madeleine had died.

Battut - an experienced journalist who has worked on a number of major inquiries - claims police believe that evidence found in the McCanns' hire car will "prove that the little girl had ingested medicines, without doubt sleeping pills, in large quantities".

A source at the newspaper claimed: "We are not simply repeating rumours carried in other papers. This is not a theory, but a fact contained in hard evidence in the hands of the Portuguese authorities.

"It is all very well putting theories and opinions forward, but in the end this case will be decided on evidence. As journalists, we have been trying to establish what evidence is available."

DNA evidence which has reportedly been found in the hire car includes hair, blood and bodily fluids which match Madeleine's.

Police are said to want to examine the vehicle again. It is currently being kept in a safe place by the family who are considering having their own tests carried out on it as they strive to prove their innocence.

Portuguese police are said to be drawing up a list of 40 new questions that they want to put to Mrs McCann. But British forensic experts expressed doubts over the claim.

Alan Baker, of the independent forensic science organisation Bericon, said: "These samples are likely to be far from ideal. If it is just a smear or dried deposit you could detect the drug but not how much."

Last night friends of the family dismissed the latest speculation. Gerry McCann reportedly told a friend: "There are large craters in every one of these theories, in these ludicrous accusations.'

"As far as Kate and I are concerned there is no evidence to suggest that Madeleine is dead. We are 100 per cent together on this, not one grain of suspicion about each other."

A close friend of Mrs McCann's said: "She is a gentle mother who loves her children very much.''