It is always possible that the US government did not follow up on these claims...

...but I doubt they failed to do so. The CIA and the other intel agencies would *never* admit that they were searching for these caches, and would never admit it if they found them.

Why? Because of the panic it would cause for all those who live nearby, the sudden end of those locations' economic value, and for the diplomatic damage it would do.

So...no. I strongly suspect the allegations were taken quite seriously, and the rest of us were never told about it. And that's as it should be, how it *must* be.