AN ALLEGED IGNITION OCCURRED ON THE 6 NORTH MAINS 088 MMU. THE JOY MINER WAS CUTTING FROM (OO TO 000) ENTRY AT 111 BLOCK. INCIDENT LASTED APPROX. 1 SECOND. ORANGE IN COLOR, APPROX. 14 TO 18 INCHES IN DIAMETER, AND WAS SELF-EXTINGUISHING. NO INJURIES OR DAMAGES OCCURRED.