Six plastic tanks each containing 1,000 litres of diesel were found on a truck in Marsaxlokk by Customs officials in the early hours of this morning.
The Customs Department said in a statement that the driver told them the diesel had been unloaded from a vessel berthed in Delimara.
The truck was sealed and is being kept at Customs and investigations are being carried out on the vessel.
The department said it has been observing and investigating several localities in Malta and Gozo for the past weeks in its fight against contraband diesel. It retained a bowser containing contraband diesel a month ago.
The police are investigating both cases.