Germans knew there was something extremely shady going on with people being deported to "work camps". But Germans had a weird notion of plausible deniability because they did not know for certain. They did not want to know either of course.

They even had a term for this: wir haben es nicht gewußt

Unadapted borrowing from German wir haben es nicht gewußt (“we did not know (it), we had no knowledge of it”).

It refers to the stereotypical defense said to have been used by Germans attempting to deflect accusations of not having done enough to stop Nazi crimes against humanity during the Second World War, especially the Holocaust.