MIB Note: the MIB archivists find it unlikely that a splinter group of the main Human race could possibly have over-come a well equipped and healthy Draconian base camp. The story is credible only if one presupposes that the Draconian mission had become dysfunctional or cut-off from its supply lines or reinforcements. Even then, one has to wonder why the caverns were not simply retaken by a fully equipped "rescue" mission later on. It is more reasonable to suppose that the caverns had actually been abandoned already, when discovered by the Humans, perhaps with technology and other materiel left behind by the Draconians, after their mission had been completed.
There are rumors that certain Drac splinter groups have attempted to retake the facility over the last couple centuries, perhaps simply for revenge rather than strategic necessity, and that this may have been partially successful. Additional reports further cite that Aghartians sometimes work as MIBs, partially as a result of these attacks. [MIBs: no comment...]
They are still in possession of technology and understandings considerably in advance of main-stream Human culture. Though primarily isolationists, the Aghartians claim to have successfully infiltrated, come to terms with, and otherwise control various Human government and industrial elements, especially in the United States, Japan and (more recently) China.
The Agharian space effort / fleet is known (to some, at least) as the 'Silver Fleet' and is of quite advanced technology, particularly when one considers that it was created by a splinter group of humans, with very little outside help beyond the original treasures gleaned from the Draconian encampment, whether won in battle or discovered abandoned.