What was found
PILOT REPORTED-AFTER TAKEOFF & PASSING THROUGH 2,000 FT, CREW RECEIVED A MASTER WARNING FOR LAV SMOKE. STOPPED THE CLIMB AT 3,000 FT AFTER ASKING THE FLIGHT ATTENDANT IF THERE WAS ANY SMOKE COMING FROM THE LAV. THE FLIGHT ATTENDANT CONFIRMED SMOKE COMING FROM LAV. CREW RAN QRH FOR LAV SMOKE & PULLED CIRCUIT BREAKERS LAV FLUSH & LAV LIGHT. DECLARED AN EMERGENCY & RETURNED TO AIRFIELD. LAV SMOKE LIGHT WENT AWAY & PLANE LANDED & RETURNED TO THE GATE. CLEANED LAV SMOKE DETECTOR IAW AMM 26-14-01, OPS CHKD GOOD. PERFORMED GVI OF LAV LIGHTS & BALLASTS, NO ISSUES NOTED, OPS CHKD GOOD. PERFOMED GVI OF THE GASPER FAN, NO ISSUES NOTED, OPS CHKD GOOD. PERFORMED OPS CHKD OF AIR CONDITIONG SYS WITH APU, & BOTH MAIN ENGS, OPS CHKD GOOD, NO SMOKE OR ODOR DETECTED. FCF C/W NO DEFECTS OR SMOKE DETECTED.