What was found
CREW REPORTED A FORWARD SMOKE IN LAV WARNING MESSAGE AFTER TAKEOFF. CREW ELECTED TO RETURN TO DAY AND LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED AND FOUND NO SIGNS OF A FIRE IN THE LAVATORY. MAINTENANCE SUSPECTS ENGINE WASH SOLUTION FOR THE CAUSE OF THE ODOR. MAINTENANCE GROUND RAN ENGINE AND BURNED OFF ALL REMNANTS OF THE SOLUTION IN ACCORDANCE WITH THE AIRCRAFT MAINTENANCE MANUAL. OPERATIONAL CHECKS WERE GOOD, NO LEAKS NOTED. AIRCRAFT WAS RELEASED FOR SERVICE.