Despite the difficulty of finding traces of this material 50 years later, in February 1990, Professor Jan Markiewicz, Director of the Institute of Forensic Research in Kraków, redid the analysis. Markiewicz and his team used microdiffusion techniques to test for cyanide in samples from the suspected gas chambers, from delousing chambers, and from control areas elsewhere within Auschwitz. The control samples tested negative, while cyanide residue was found in high concentrations in the delousing chambers, and lower concentrations in the homicidal gas chambers. This is consistent with the amounts required to kill lice and humans.