Reinc,
Not sure which biologic process would be involved in breaking down the cyanide remains but it is made of sodium, nitrogen, carbon, and oxygen. I doubt there would be anything toxic left after break down. It is only poisonous in the blood because it prevents oxygen from being transported. After the carbon in the original process was pulled into the steel most of the remains in the boxes would not have been "cyanide" anyway.

BR,  I am glad there is not enough info in the articles to duplicate a Krag, otherwise I would have to start telling myself I am too old to start a project like that. Anyway thanks as it is interesting info.