As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU 6 PACK LIGHT ON, SEEMS TO BE INDICATION PROBLEM. INSPECTED TAIL AREA OF A/C IN BALLPARK, DEPARTED MEL 49-01. AFTER T/O F/A REPORTED BURNING ODOR, DECLARED EMERGENCY, AIR RETURN TO DEPARTURE. ACCOMPLISHED CONDITIONAL INSPECTION IAW CARD 05-51-26-800-801C1. NO SOURCE OF BURNING ODOR FOUND. ACFT OK FOR SERVICE. APU OPERATION AND INDICATION ALL NORMAL.