Tannerite is, though. (And where it isn't, blasting charges for mining are. And where those aren't, fertilizer probably still is. Explosives are hard, yet also far easier than you'd think)
For instance; https://pubs.acs.org/doi/abs/10.1021/cen-v073n022.p006
If you show up at a farm store to buy certain fertilizers in unusual quantities, that interaction will likely be reported or otherwise flagged.