In the last phase of the camp operations, all prior mass graves were unearthed by a mechanical digger. It was the result of direct orders from the Nazi leadership (possibly from Himmler), soon after the Soviet Katyn massacre of 22,000 Polish soldiers was discovered in Russia. At Katyn, the German-led exhumations by the international Katyn Commission revealed details of the mass murder by examining preserved bodies. The Germans attempted to use the commission's results to drive a wedge between the Allies. All corpses buried at Bełżec were secretly exhumed and then gradually cremated on long open-air pyres, part of the country-wide plan known as the "Sonderaktion 1005". Bone fragments were pulverised and mixed with the ashes to hide the evidence of mass murder. The site was planted with small firs and wild lupines and all camp structures were dismantled.