As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING DESCENT INTO ATL TRANSFERRED THE PACKS TO THE APU AND IMMEDIATELY NOTICED A BURNING ODOR. TRACES OF SMOKE WERE VISABLE IN THE COCKPIT AND RECEIVED A SMOKE TOILET CAUTION. NO EXCESS SMOKE WAS OBSERVED IN THE LAV. SHUT OFF THE PACKS, SMOKE DISSIPATED. EMERGENCY DECLARED, TRUCKS REQUESTED TO BE ON STANDBY AS A PRECATION.