What was found
SMELL OF FUEL IN CABIN. FLIGHT LEG ABORTED AND RETURNED TO AIRPORT. MECHANIC NOTIFIED AND RESPONDED. CHECKED ALL COMPONENTS AND AREAS OF HELICOPTER FOR SOURCE. NO FUEL LOCATED IN OR AROUND AIRCRAFT OR STRUCTURES, CABINS, COMPARTMENTS. PERFORMED ENGINE RUN-UP WITH NO ODOR OF FUEL. PERFORMED MX FLIGHT, NO ODOR DETECTED. UNABLE TO DUPLICATE ISSUE. ALL CONNECTIONS, COMPARTMENTS, AND AREAS FREE OF FLUID AND ODORS.