The semi-industrial incineration of corpses at the Treblinka extermination camp began as soon as the political danger associated with the earlier burials was realised. In 1943, the 22,000 Polish victims of the Soviet Katyn massacre were discovered near Smolensk and reported to Adolf Hitler. Their remains were well preserved underground, attesting to the Soviet mass murder. By April 1943, Nazi propaganda began to draw attention of the international community to that war crime. The Katyn Commission was formed to make detailed examinations in an effort to drive a wedge between the Allies. Meanwhile, the secret orders to exhume mass graves and instead to burn the hundreds of thousands of victims came directly from the Nazi leadership in April. The corpses that had been buried at Treblinka with the use of a crawler excavator were dug up and cremated on the orders of Heinrich Himmler himself, who visited the camp in March 1943. The instructions to utilise rails as grates came from Herbert Floss, the camp's cremation expert. The bodies were placed on cremation pyres that were up to long, with rails laid across the pits on concrete blocks. They were splashed with petrol over wood and burned in one massive blaze attended by roughly 300 prisoners, who operated the pyres. In Bełżec, the round-the-clock operation lasted until March 1943. In Treblinka, it went on at full speed until the end of July.