What was found
AIRCRAFT WAS GROUNDED. SHORTLY AFTER TAKE OFF FLIGHT ATTENDANTS NOTICED A LIGHT SMOKE IN CABIN. EMERGENCY WAS DECLARED AND AIRCRAFT RETURNED TO BLOCK, LANDED OVERWEIGHT AND WITHOUT INCIDENT. FLIGHT WAS CANCELLED. NO PASSENGERS OR CREW REPORTED ILLNESS DUE TO SMOKE. FOUND APU OIL RESERVOIR CAP GASKET LEAKING. REPLACED GASKET, CLEANED APU INLET OF EXCESS OIL. PERFORMED MCM CARD 21-92-12 AND 05-96-70. NO ODOR OR SMOKE IN CABIN NOTED. A/C DID NOT EXCEED OVERWEIGHT LANDING OF 130,000 LBS.