As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FORWARD PART OF PASSENGER CABIN FILLED WITH SMOKE. THE SMOKE APPEARED WHEN THE LEFT PACK WAS RUNNING ON THE NR 2 ENGINE BLEED. SUPPLEMENTAL DATA UPDATE, CAPTAIN REPORTED NO SMOKE IN THE COCKPIT. SMOKE STARTED JUST BEFORE SWITCHING BLEEDS. THE PACK DID NOT OVERHEAT. RAN ALL THREE ENGINES FOR 20 MINUTES. NR 3 BLEED RUNNING RIGHT PACK THEN LEFT PACK. NO SMOKE IN CABIN NOTED.