What was found
AIR TURN BACK. FLIGHT CREW REPORTED SMOKE IN CABIN SHORTLY AFTER TAKEOFF, JUST AFTER APU BLEED WAS TURNED OFF. AIRCRAFT LANDED WITHOUT INCIDENT. COMPLIED WITH MM 71-00-00-810-802. PERFORMED OPS CHECK AND COULD NOT DUPLICATE DISCREPANCY ON GROUND. PERFORMED TEST FLIGHT. PERFORMED NORMAL BLEED-OFF TAKEOFF AND REINSTATED BLEED CONFIGURATION IAW NORMAL TAKEOFF/CLIMB PROCEDURES. MONITORED CABIN AND COCKPIT FOR SMOKE, MIST INDICATIONS. CHECKED NORMAL, NO DISCREPANCIES FOUND.