It was pretty old movie 70s-90s, about a military sent to investigate a remote island with strange signals, or crashed survivors on an island[cant remember exactly]. When the team landed it became apparent that it was some UFO underground.I remember there was a concrete structure, or the team discussed about filling the ufo with concrete. There was a forcefield preventing the access, a telepathic experience, where alien set survivors against each other, and an alien drilling into the head of one of soldiers. There was either no alien inside, or the alien was the short gray/green typical one. I think its Xtro 3, but if you have other picks then please share.