EU inspectors, hoping to prevent any recurrence of customs fraud, will beef up checks of goods originating in Serbia and Montenegro that are imported under preferential terms, the bloc's Official Journal said on Monday.
"Although the management and control of preferential origin appears to have improved, the administrative co-operation provided for the verification of origin certificates issued in the past has been slow and not always conclusive," it said.
"Consequently, the Commission will continue to apply a reinforced surveillance of Serbia and Montenegro with regard to their implementation and control of preferential origin."
Under special concessions designed to boost the economic recovery of the western Balkans region from wars in the 1990s, Serbia and Montenegro may export many goods duty-free to the EU.
Sugar is a prime example of where the scheme went wrong.
Serbia and Montenegro only recently won back the right to send duty-free sugar to EU markets, ending a 15-month row over fraudulent imports as of August 7.
Serbian officials say they hope to ship $100 million of sugar to the EU in the next year.