As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAD - CREW REPORTED SMOKE IN THE CABIN DURING FLIGHT. EMERGENCY DECLARED FLIGHT RETURNED IAD LANDED WITHOUT INCIDENT. ACCOMPLISHED INSPECTION OF APU AND ENGINES NO LEAKS NOTED. ACCOMPLISHED CARD 21-92-12. SYSTEM GROUND CHECK NORMAL OPERATION.