As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
YEG - AIRCRAFT RETURNED TO FIELD WHEN THE LAVATORY SMOKE DETECTOR SOUNDED. DURING INSPECTION OF APU AN EXTERNAL OIL LEAK WAS NOTED. MAINTENANCE INSPECTED THE ACM PACK CONDENSER SOCKS FOR OIL CONTAMINATION. NONE WAS NOTED. PRESSURIZED AND RAN AIRCRAFT WITH PACKS AT FULL HOT FOR 20 MINUTES. NO SMOKE WAS NOTED AND SMOKE DETECTOR DID NOT SOUND. AIRCRAFT RETURNED TO SERVICE.