According to the official memorial website the number of stones was doubled in 1998 and then more added after that. It specifically states that concrete was poured over the alleged location of human ashes. https://muzeumtreblinka.eu/en/informacje/commemoration/ This is a revisionist eyewitness account of the memorial. https://furtherglory.wordpress.com/2016/02/24/monuments-at-treblinka-prevent-digging-for-evidence/ This is an interesting article from the "Official Narrative" camp lamenting the lack of a true forensic examination of the site. An interesting tidbit: The excuse provided by (((officials))) for covering over the alleged site of human remains was to prevent "grave robbing". https://holocaustcontroversies.blogspot.com/2010/05/mass-graves-at-nazi-extermination-camps.html#_Treblinka

jews poured concrete over the entirety of the area. It's a literal cover up.