EE 3RD SHIFT PLANT MECH. WAS CUTTING METAL WITH A TORCH IN A VESSEL ON THE 3RD FLOOR. TWO RUBBER MIXING LINES WERE BESIDE WHERE CUTTING WAS TAKING PLACE. A SMALL FIRE STARTED ON THE RUBBER MIX ING LINE AND EE GOT A FIRE EXTINGUISH TO EXTINGUISH THE FIRE AT THIS TIME AN IGNITION OCCURRED INT HE MIXING LINE ACETYLENE OR UNKNOWN GAS. THE FIRE WAS EXTINGUISHED AND THERE WAS NO INJURIES