A sunken vessel that became an explosives trove for the Mafia has been sealed shut by Italian authorities in an undersea operation. Italian freighter Laura Cosulich was torpedoed by British submarine HMS Upholder in 1941, as it travelled towards Libya.

Its wreckage has since lay at the bottom of the Mediterranean Sea some 50m underwater off the Calabrian coast near Capo D'Armi, the south-western tip the Italian peninsula. According to official documents, the ship that had set sail from Venice was carrying innocuous goods including fabrics, spirits and machine tools, when it went down.

However, after the sunken hull was located in the 1970s, it was discovered that 1,500 tonnes of TNT and other military supplies for fascist troops in northern Africa were hidden amid the cargo. The finding didn't go unnoticed by the local mafia syndicate, the 'Ndrangheta, which has since become Europe's largest drug cartel.

Throughout the 1990s and 2000s explosives from the Laura Cosulich were often seized by anti-Mafia police targeting Calabrian clans, suggesting Mafia divers had been retrieving large quantities of TNT from the wreckage.

The ship became infamously known as the mob's underwater explosives depot. As recently as February 2015, eight people were jailed for trafficking nitroglycerine from the freighter, with anti-Mafia prosecutor Cafiero de Raho describing it as the 'Ndrangheta bombs "supermarket".

A complex plan to put the cargo out of criminals' reach, was subsequently launched by authorities. After months of planning, navy divers successfully blocked access to the Laura Cosulich's hold with concrete bags and an iron cage.

The Italian navy said it took officers 67 hours of working underwater spread over dozens of 50-minute dives to completely seal off the cargo. "It hasn't been easy as working conditions were very difficult at more than 50m in depth," said Admiral Eduardo Serra. De Raho said it was a "great result" in the fight against organised crime.

Laura Cosulich Mafia underwater explosives depot
Italian navy divers have blocked access to the TNT cargo of a WWII ship that was being raided by the Mafia Italian Navy