As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RETURNED TO GATE, SMOKE WAS DETECTED IN THE PASSENGER CABIN. AS PER FIM 21-00-01 PAGE 109 ITEM 6 PROCEDURE 4 WAS PERFORMED CHECK TO THE LT & RT RECIRCULATION FAN FILTERS. AS PER AMM 21-25-02 PAGE 401 THE PREFILTER ON RT RECIRCULATION FAN WAS REPLACED AND FILTER ON LT RECIRCULATION FAN WAS CLEANED. OPERATIONAL TEST WAS PERFORMED WITH SATISFACTORY RESULTS AS PER AMM 21-25-00.