What was found
AFTER ROTATION OUT OF IND, STARTED TO SMELL FUMES. THERE WAS NO EVIDENCE OF SMOKE IN THE CABIN BUT THE F/A REPORTED THE ODOR WAS STRONGER IN THE FRONT. DECISION WAS MADE TO RETURN TO IND. THE ODOR DID START TO DISSIPATE DURING LANDED. MAINTENANCE CHECKED THE AIRCRAFT AND ADVISED NR 1 ENGINE WAS JUST REPLACED AND THE ODOR POTENTIALLY WAS DUE TO THE NEW ENGINE. NO EVIDENCE AT ALL FOR ANY OTHER CAUSE OF THE SMELL. ACFT RETURNED TO SERVICE.