I'm wondering what was known or rumored in local places near the larger extermination camps like Auschwitz-Birkenau or Treblinka. There would have been massive numbers of trains with very strange looking cars (yes I know they mainly traveled through cities at night). There would have been black smoke belching out at all hours, also sometimes outdoor pyres of incomplete human cremation which must have smelled characteristically organic. And occasionally a few escapees.

Surely there would have been some clues dropped here and there as to what was going on? Rumors must have flown? Note, I'm not asking to place blame on locals for not interfering and risking death themselves. Just curious about it is all.