Investigators in the west German town of Grevenbroich started DNA tests on hundreds of men on Saturday 23rd November in the hope of solving a 23-year-old murder cold case.
Claudia Ruf, 11, was found sexually assaulted and murdered 70km (43 miles) south of the town in 1996. No-one has been charged with her death.
Police sent invitations to at least 900 men in an effort to match DNA samples recovered from the scene.
Those who agreed had saliva swabs taken at a local primary school, where the samples were being collected.
Claudia Ruf was kidnapped in May 1996 while walking a neighbour's dog in Grevenbroich, which is about 40km north-west of Cologne.
Her body was found two days later having been strangled, doused in petrol and partially burned.