As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI AFT CARGO SMOKE ECAM INDICATION ILLUMINATED AND DISCHARGED EXTINGUISHING AGENT. AIRCRAFT RETURNED TO THE GATE AND FIRE DEPARTMENT INVESTIGATED SOURCE OF INDICATION. NO DETECTION OF FIRE OR SMOKE NOTED. MAINTENANCE VERIFIED NO EVIDENCE OF FIRE OR SMOKE AND REPLACED THE FIRE EXTINGUISHING BOTTLE. SYSTEM OPERATION CHECKED NORMAL.