What was found
REPORTED A STRONG NON BURNING, DIRTY SOCK ODOR, IN THE CABIN. THE ACFT WAS REMOVED FROM SERVICE AND TSM 05-50-00-81-08-31A AND 49-00-81-81-08-47 WERE ACCOMPLISHED. RESIDUAL OIL WAS FOUND IN THE APU COMPARTMENT, NO ACTIVE LEAKS NOTED. THE APU COMPARTMENT AND APU INLET DUCT WERE CLEANED AND THE ACFT WAS RETURNED TO SERVICE. NO FURTHER ISSUES REPORTED ON SUBSEQUENT FLIGHTS.