As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW - FLT 61 - EN ROUTE DFW-NRT - IN CRUISE AN UNIDENTIFIABLE STRONG NOXIOUS ODOR DETECTED ONBOARD. AIR INTERRUPTED AND RETURNED TO DFW. LANDED WITHOUT INCIDENT. TROUBLESHOT AIR CONDITIONING DUCTING AND LIGHTING FIXTURES IN CABIN AND FORWARD CARGO AREAS. NO DISCREPANCIES FOUND. SYSTEM GROUND CHECKED NORMAL OPERATION. (M)