As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEA - DURING DESCENT, SMOKE WAS OBSERVED IN CABIN AND COCKPIT. TURNING OFF THE NR 1 BLEED STOPPED THE SMOKE. MAINTENANCE GROUND RAN AIRCRAFT AT 90 PERCENT TORQUE WITH THE BLEEDS ON, BLEED FLOW TO MAXIMUM AND THEN TO BLEEDS OFF, BLEED FLOW TO MAXIMUM AND AT VARIOUS OTHER POWER SETTINGS. COULD NOT DUPLICATE DISCREPANCY. AIRCRAFT RETURNED TO SERVICE.