THE NO 1 UNIT (MMU001-0) EXPERIENCED A METHANE OR DUST IGNITION IN THE FACE OF THE NO 1 ENTRY, LEFT SIDE OF CUT, THE CUT WAS APPROX. 15' DEEP. THE EYEWITNESS OBSERVED A YELLOW GLOW IN THE FAR LEFT CORNER OF THE FACE. THE DURATION OF THE GLOW WAS 2-3 SECONDS. THERE WERE NO INJURIES FROM THE INCIDENT.