ROOF BOLTER OPERATOR WAS INSERTING A BOLT INTO A BOLT HOLE. AS THE BOLT WAS PUSHED INTO THE HOLE, IT WAS BEING SPUN AT HIGH RPM TO MIX THE RESIN. AFTER SPINNING FOR THE REQ'D TIME, THE BOLT WAS THRUST UPWARD INTO THE HOLE. AS IT WENT UP, A SPARK WAS CAUSED AND A FIST SIZED BALL OF FLAME WAS OBSERVED. FLAME LASTED APPROX. 15 SECONDS LOCATION- NO.3 ENTRY XCUT 53, MMU-001-0