A FALL OF GROUND OF APPROX. 30 TONS OCCURRED AT THE INTERSECTION OF C52-D4 & THE CENTRAL ORE DRIFT DURING A SHIFT WHEN NO PERSONNEL WERE WORKING UNDERGROUND. FALL WAS IMMEDIATELY ADJACENT TO AN AREA THE CREW HAD BEEN INSTALLING GROUND SUPPORT IN BUT DID NOT INVOLVE THE AREA WHICH HAD ALREADY BEEN SUPPORTED. NO EQUIP. DAMAGE OCCURRED. MSHA WAS NOTIFIED BY PHONE.