As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB, FUMES WERE REPORTED IN THE CABIN. FLIGHT CREW RETURNED AIRCRAFT TO DEPARTURE AIRPORT. MAINTENANCE INSPECTED THE ENGINES, APU, AND AC PNEUMATIC DUCTING SYSTEM AND COMPONENTS. APU WAS PLACED ON MEL AND AC PACK SYSTEM BURNOUT PROCEDURES WERE PERFORMED.