What was found
RECEIVED SMOKE AFT AFT WARNING MESSAGE. COMPLETED QRH AND RETURNED TO FIELD. FLIGHT ATTENDANTS AND PILOTS NOTICED FUMES BUT NO SMOKE IN CABIN (FLT#3210) CLOSED AFTER SOME INVESTIGATION, FOUND THE A #1 ENGINE COMPRESSOR WASH WAS COMPLETED THE PREVIOUS NIGHT PRIOR TO THE EVEN FLIGHT. FOLLOWED FIM PROCEDURE FOR ABNORMAL SMOKE/SMELL AFTER MAIN ENGINE COMPRESSOR WASH IAW FIM. COMPLIED WITH #1 ENGINE DRYING PROCEDURE PER AMM. ABNORMAL SMOKE/SMELL NO LONGER PRESENT.