As is the case with many types of important discoveries, the less the public knows about it, the better. Not because of anything nefarious, but because people steal things. These discoveries need to be done slowly and methodically. Everything needs to be catalogued. I’m not sure what the point of a cover-up would be, but we are dealing with a government not known for its candor.
If there is a hollow, some raghead might decide to destroy it with explosives. They destroy everything else they touch.