As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX - FLIGHT 2129. FLIGHT ATTENDANT REPORTS A "FOG" COMING FROM THE LAST 3 ROWS FROM ENG START THROUGH 10,000, THEN DISAPPEARED. MAINTENANCE PERFORMED A GROUND RUN OF THE ENGS WITH INDEPENDENT USE OF THE BLEED AIR. NO FOG, OR OTHER DEFECTS NOTED. RETURNED TO SERVICE. NO PARTS REPLACED. (S)