Gassing wouldn't become wholesale until well into 1942; and would only be referred to by the euphemism of 'Processing' or something similar.

Now, as to your actual question; it would be quite impossible. The SS jealously guarded their realms of command, and it was hard enough for the Wehrmacht to argue that Waffen SS and Luftwaffe Feld formations would need to be under their command for the sake of sanity and ease in the C2 links. So you 'investigating' would get you a few curt words at the door and sent off on your way with directions back to your command post, because surely you were lost. Almost 1000 miles a bit West of your most likely position for an Ostkampf formation, in fact.

More realistically, you could perhaps investigate the actions of Einsatzgruppen if you're an Ostkampfer; and perhaps feebly protest the mass extermination of Jewish peoples and youth, as did Helmuth Groscruth and certain Chaplains in the 6.Armee. None of your actions would matter very much, in the end, and in all reality as a Wehrmacht General you probably have already issued the Commisar and Bolshevik-Jew orders to your Divisional and Regimental commanders, and are fully aware of the atrocities being committed in your immediate rear.

Hope that answers your question :)