How did Hitler try to cover up mass death in the first year the camps opened?

Answer 1

Please note that the cover up lasted for the entire period 1941-45.

The victims weren't told they were being sent to death camps, simply that they were being "relocated". In the early stages, they sometimes had to send postcards to any next of kin still at home to say that they had arrived safely.

Incidentally, the extermination camps were located in Poland; they weren't just down the road from Germany as it were.

Towards the end, they hid the camps by burying the bodies, planting trees, etc.

Answer 2

many Jews believed they were only being deported and that death camps were simply refugee camps until new home was found. They also did not believe the rumours aout the camps as they were a big economic force in Gemany, especially with the war. Hitler disguised the camps as factories (often rubber factories) saying the Jews were forced labourers (also explains the smell). Allies only heard rumours and could not really retaliate anyway. They could not go by sea, or risk the swarms of U-boats. They could not bomb the camps or risk more death. Land was only option and they were doing that anyway.