A suspected contraband fuel operation at sea was foiled by the armed forces after an “accidental” oil spill prompted an investigation.

Sources said the alleged diesel smuggling was uncovered on Monday after an aircraft on routine patrol spotted a ship leaking fuel some 30 nautical miles south of the island.

The fuel courier Alice was carrying more than 80,000 litres of Libyan diesel intended for a legal ship-to-ship transfer to another locally registered vessel, Santa Maria.

Two patrol boats were sent to the Alice and an armed forces boarding team reported the ship was leaking fuel, the AFM said.

Marine pollution of this nature is regarded as a criminal offence and the incident was reported to the police, the AFM added.

The fluid started gushing out of the ship’s oil transfer nozzle after crew members allegedly attempted to siphon off fuel into large drums, sources said.

The sources said the crew members told investigating officers that the spill had resulted from “an accident” during the oil-transfer process. The Alice, the Santa Maria and two other vessels suspected of being engaged in fuel transfers, Sliver King and Xmun, were escorted into the Grand Harbour by the armed forces along with 28 crew members who were taken in for questioning. A 56-year-old Maltese man from the Alice was among them.

Customs officials also tested the quality of the fuel and searched the vessels for contraband.