As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 4274 THE CREW REPORTED A BAD ODOR COMING FROM PACKS, SMELLED LIKE GYM SOCKS. THE AIRCRAFT WAS REMOVED FROM SERVICE. CLEANED BLEED SYSTEM FROM PACK 1 SYSTEM IAW EMB AMM 21-20-00 STEP (J) 1-18. THE OPERATIONAL CHECK WAS GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.