A ROOF FALL WAS OBSERVED BY MSHA INSPECTORS DURING A REGULAR INSPECTION . THE FALL MEASURED 20' WIDE BY 100' LONG BY 7'HIGH. THE FALL OVER RODE TEMPORARY SUPPORTS IN A PREVIOUS FALL AND INTO T HE TRAVELWAY TO MPL#2. VENTILATION WAS NOT AFFECTED. PASSAGE TO MPL#2 WAS AFFECTED UNTIL ADDITIONAL SUPPORTS WERE ADDED. NO PERSONS WERE INJUREDAS A RESULT OF THE FALL.