As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
HKG FLT 192 EN-ROUTE HKG - LAX. THE AIRCRAFT WAS GROUNDED. DURING PUSHBACK, GROUND INFORMED US OF SMOKE FROM THE APU. WE WENT BACK TO THE GATE DURING THE APU AUTO SHUTDOWN WITH NO FIRE INDICATION. SMOKE CONTINUE FROM TAILPIPE AS A SMALL FIRE COULD BE SEEN BY MAINT IN THE TAILPIPE. THE APU WAS PLACED ON MEL DEFERRAL. MAINTENANCE ACCOMPLISHED AN APU CHANGE PER MCM CARD 49-94-12 AND EA 279880B.