'Narco-torpedoes' and frogmen: drug smuggling ring busted in Rotterdam Two of them were linked to Marco Armando, 56, considered one of the masterminds of a 1992 heist in which 146 million francs (£14.6 million) were stolen from a branch of the Bank of France. He was sentenced to 18 years in prison in 1996 but let out in 2005. Another was Jean-Michel Dominici, brother of Corsican gangster Ange-Philippe Dominici, convicted to 14 years in 2010 for his part in the theft of 3,000 gold ingots from Swiss precious metals firm Metalor in 2004. The bullion has never been recovered. Police watched with growing incredulity as more underwater reconnaissance missions were conducted. "When we saw these people training with autonomous diving gear, submersibles and inflatable parachutes to refloat heavy objects from the depths, we wondered what the hell are they up to?," Mr Frizon told the Daily Telegraph. Given some of these people's past form in Europe's criminal underworld and their sudden taste for tourism in South America, we decided to take a much closer look. Police tracked Mr Armando for a year, finally trailing him and two associates as they drove from southern France to Rotterdam via Paris and Antwerp on April 16 in rented cars loaded with heavy diving equipment. The men never reached open water. Tipped off by their French colleagues, Dutch police arrested the suspects and seized their gear, including two propulsion vehicles and inflatable parachutes. In a metal cradle attached to the hull of the Delta Laguna, a Dutch cargo ship that departed from Venezuela with a stop in Curacao in the Dutch Caribbean, police found a rusting torpedo-shaped metal tube over 8 feet long, stuffed with cocaine worth up to 7 million euros on the street. Nine other suspects were arrested in France - two in Corsica, five in Nice, one in Marseille and one in Toulouse. They found weapons and a cocaine workshop. In all five were placed under formal investigation on drug trafficking charges. Mr Frizon said anti-narcotic police in Colombia and Peru had first alerted him to the torpedo technique around three years ago. We knew drug cartels were looking for safer ways of transporting their wares. Air travel is problematic when it passes via Africa while cargo ships are at the mercy of customs checks on the surface," he said. Another ploy was to attach drug-filled mini-submarines to the back of cargo vessels via a metal cable, but these were easily spotted. So they developed this new method. He said the cocaine came from Peru and Colombia and was likely destined for sale in Paris and southern France. Police believe Mr Armando to have masterminded the "narco-torpedo" operation. The three divers are due to be transferred back to France in the coming weeks. Five of those questioned have been placed under formal investigation on suspicion of belonging to the ring. The inquiry is ongoing. Police said the scheme had likely been ongoing for years with a transatlantic trip every six months, and that he could not rule out the possibility that the team his men were tracking managed to smuggle in cocaine even under surveillance. "We are the first to have caught a team in the act but it's almost certain others are or have been doing the same thing," said Bernard Mascarelli of Nice judicial police. When asked whether such a technique might be in use in British ports, he said: "Absolutely."