As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 4774, CREW REPORTED O2 MASKS DEPLOYED UNCOMMENTED ON GROUND. SOME MAY HAVE ACTIVATED IN THE REAR. AIRCRAFT REMOVED FROM SERVICE. INSPECTED EACH O2 MASK AND OXYGEN GENERATOR AND STOWED IAW EMB AMM 35-20-04. ALL GENERATORS IN SERVICEABLE CONDITION. AIRCRAFT RETURNED TO SERVICE.