AFTER DRILLING A HOLE FOR WATER IN AN ABANDONED MINE (#6 HIGHWALL) AN IGNITION WHILE CUTTING A WALL CASING. THE PIPE WAS APPROX 11 FT ABOVE THE GROUND AND WAS 10 INCHES IN DIAMETER. WHILE CUTT ING THE PIPE, A PIECE OF HOT METAL ON A SPARK FELL IN THE HOLE CAUSING AN IGNITION. A GUSH OF AIR WAS REPORTED, NO FLAMES.