As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON TAXI OUT, APU FAILED WHICH RESULTED IN SMOKE IN THE CABIN. FLIGHT CREW DECLARED AN EMERGENCY AND CALLED. NO EVIDENCE OF FIRE WAS FOUND AND THE SMOKE CLEARED. CFR CLEARED AIRCRAFT TO TAXI BACK TO THE GATE. MAINT DEFERRED THE APU AND THE AIRCRAFT WAS RELEASED FOR SERVICE. (K)