In 1996, the 11-year-old Claudia Ruf kidnapped, raped and strangled to death.

the Perpetrator escaped, and therefore have the German police now invited 900 men, who were between 14 and 70 years of age at the time of the offence, to provide a voluntary DNA sample.

Claudia Ruf disappeared when she went to walk with his neighbor's dog in Grevenbroich, located in Germany between Düsseldorf and Cologne. Two days later she was found murdered, writes dpa.

Police now believe to have been important clues that can lead them far in the investigation.

It is the reason why they now make the large DNA collection, which started today, Saturday, where hundreds of men met up at a local school to drop off their sample.

the DNA collection happening Avrupabet soon after, Claudia Rufs father, Friedhelm Ruf, shared an emotional video on social media.

"After more than 23 years, there is a great chance to unravel the sad fate, my daughter led," he says in the video according to the AP, and continues:

"the Perpetrator has been able to hide for too long behind all of us."

Police do not expect that the offender will voluntarily appear and submit a DNA sample, but they hope that one of his family members, and thereby can lead the police on the track.

It is the second time in 10 years that the police collect DNA samples from men in the local area.

the First time was back in 2010, which was collected the DNA from the 350 men.

It is not clear whether the 350 must submit a test again, or on the old DNA-profiles can continue to be used.