As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RETURNED TO YYZ AND CANCELLED DUE TO SMOKE IN THE CABIN. UNITED DISCOVERED THE INTERNAL BOOSTER SPOOL CAVITY SURFACES BADLY BATTERED FROM WHAT APPEARS TO BE LIBERATED BOLT HEADS COMING OFF AFT BLADE RETAINER FASTENERS AND PUNCTURING 1-2 BEARING SUPPORT OIL TUBES CAUSING THE OIL LEAK AND SUBSEQUENT SMOKE IN THE CABIN. PARTS WERE SENT TO GE FOR INVESTIGATION. SR 7-1-248442576 (ON-GOING INVESTIGATION).