THE MAINTENANCE FOREMAN AND A MECHANIC WERE PERFORMING MAINTENANCE ON A REMOTE CONTROL MINER. THET BOTH EXAMINED THEIR WORK AREA AND THEY STATED THAT IT LOOKED SAFE. WHILE WORKING ON THE MIN ER, A LARGE PIECE OF RIB FELL WITHOUT WARNING AND LANDED ON THE SUPERVISOR'S RIGHT LEG AND LEFT ANKLE. THE X-RAY WAS NEGATIVE, BUT THERE WAS A SEVERE BRUISE TO MUSCLE ON THE RIGHT LEG.