The German prosecutor in charge of the Madeleine McCann case has said authorities there will continue investigating the British girl's disappearance as long as necessary, with no expense spared.
"Money doesn't come into it," Hans Christian Wolter of the Braunschweig prosecutor's office told the Sunday Independent. "From our perspective, as long as the investigation has a chance of success we will continue it.
"Our job is to try to get a result. If there is nothing more to investigate, of course the case will be closed, we won't keep it open needlessly. But there is no finish line in sight and at the moment we can't say how much longer it will go on. It could, theoretically, take years."
The recent public appeal for further information on Christian Brueckner, a German with a history of sexual offences against children, resulted in around 100 potentially useful tips from the public.
"How much value we are attaching to these I can't say, but everything is being followed up," Wolter said.
Reports that the swimming costumes of young girls were found at the man's apartment are not relevant to the Madeleine investigation, he added.
"That concerned a case from some years back and was carried out by the prosecutor in Halle. It is not connected to the Maddie case.
"There was a search and seizure, which we know about, but unfortunately I can't give details about that."
Madeleine's parents, Kate and Gerry McCann, released a statement last week, saying: "The widely reported news that we have a received a letter from the German authorities that states there is evidence or proof that Madeleine is dead is false."
Wolter says that in fact two letters were sent from German police to their British counterparts, and it was up to the British police to pass these letters on to the McCanns.
"There was contact between the German prosecutor and the family but that went via the police in the UK. We would say to the British police that they should please forward this correspondence on to the McCanns," he said.
Wolter says his office is appealing for Irish tourists who were in Praia da Luz, the Portuguese resort where Madeleine went missing in the summer of 2007, to come forward.
"We know for sure there were many English-speaking tourists, some of whom were Irish, in the area at that time and some of them may remember something of significance. We hope they can now examine their memory," he said.