This happened recently, a HUGE UFO with the size of a block in width and over a mile of lenght entered through the opening of mexican volcano called "Popocatepetl" just moments after it exhaled magma and steam!
And here's something curious that was caught by the metheorologic system the same day:
Some friends had as a homework to edit a video with an UFO in After Effects and send them to this crazy ass Televisa man (don't remember his name, but his program was Tercer Milenio?) and see what happened.