As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD INFLIGHT T9673/4 MAR TEST FLIGHT FUMES IN CABIN SHORTLY AFTER TAKEOFF. VISIBLE BLUE SMOKE COMING FROM AFT CABIN, QUICKLY FILLED ENTIRE CABIN. TURNED OFF AIR CONDITIONER PACKS. SMOKE SLOWLY DISSIPATED. LANDED, DECLARED EMERGENCY LANDING DURING TEST FLIGHT. FOUND OIL LEAKING FROM APU. REPLACED APU. SYSTEM GROUND CHECKED NORMAL OPERATION. (CLOSED)