As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 2491 - EWR - CREW REPORTED STRONG SMELL IN CABIN AND FLIGHT DECK. CREW PERFORMED AN AIR RETURN AND LANDED UNEVENTFULLY. EWR MX PERFORMED VISUAL INSPECTION OF BOTH ENGINE INLET ZERO BEARING AND NO OIL LEAK WAS FOUND. MX ALSO RUN APU, AND BOTH ENGINES AND BOTH PACKS, BUT COULD NOT DUPLICATE THE SMELL. PERFORMED ICE TEST, BUT COULD NOT DUPLICATE THE SMELL. ACFT WAS APPROVED TO RETURN TO SERVICE.