German prosecutors say they may have to drop the investigation into a convicted paedophile suspected of killing Madeleine McCann if they do not receive more information from the public.

Investigators told the BBC they have substantial evidence that Madeleine is dead - but this is not enough to take the suspect to court.

The three-year-old disappeared while on holiday in Portugal in 2007.

The suspect, 43, has been named by German media as Christian B.

Hans Christian Wolters, a prosecutor in the city of Braunschweig - where detectives are leading the investigation - told the BBC: "We have evidence against the accused which leads us to believe that he really killed Madeleine but this evidence is not strong enough at the moment to take him to court."

The evidence is "strong enough to say that the girl is dead and strong enough to accuse a specific individual of murder - that strong", he said.

However he added: "One has to be honest and remain open to the possibility that our investigation could end without a charge, that it ends like the others have.

"We are optimistic it will be different for us but for that we need more information."