Remember, the Chabad is probably one of the richest organizations in the world, there is no need for them to have any operations underground except to hide crimes against humanity. Notice that they had a water pump installed. A lot of men's pants hanging to dry on the railing, why? Probably they use the dirt mound is used for microbes to consume any organic materials, and the extra pants are when they need to retrieve what remains like bones. This is probably why they need a water pump too, to keep the mound moist. Forensics.