Latin American cocaine traffickers may be using submarines to move the Europe-bound drugs across the Atlantic Ocean, a top official said Monday during a conference aimed at stemming the flow of the drugs through Africa.

Alexandre Schmidt, the head of the West African branch of the United Nations Office on Drugs and Crime, said drug cartels are known to have already used submarines off the South American and Caribbean coast. Even though no submarines have been seized in West African waters, there is anecdotal evidence to suggest they are in use there as well, he said.

"We are not talking about military vessels here, but rather smaller ones which can be bought freely on the international market by anybody who has a couple of million dollars to spare," said Schmidt, who spoke during the inaugural session of a policy committee, dubbed the West Africa Coast Initiative.

The initiative was launched in 2009, after a United Nations report showed that the illicit flow of cocaine through the region boomed, surpassing even the GDP of some of the countries through which the drugs were trafficked.

West Africa became a stopover point for drug cartels after demand began to wane in North America at the same time prices soared in Europe, prompting the traffickers to shift their operation.

Due to tightened airport and maritime controls in Europe, the traffickers needed to find a halfway point. Experts say that the drugs were first brought to West Africa in small boats, then twin-engine planes. They landed on deserted islands and abandoned runways, before being parceled out to be carried north.

The cartels took advantage of corrupt institutions and lax law-enforcement, and in some countries they operated with the complicity of ruling families.

The trade evolved with the use of cargo planes, first discovered in November 2009 when a Boeing 727 landed in the Malian desert, miles from the nearest town or commercial airport. When authorities arrived, the aircraft had already been set alight, prompting authorities to speculate that it was being used to carry cocaine.

The lightweight submarines could be the latest evolution of the trade, said Schmidt. He pointed out that cocaine seizures have gone down throughout the region, at the same time that consumption in West Africa is going up.

What that shows, he said, is that the actual trade is likely increasing and that the cartels are simply becoming more sophisticated at hiding their operation.

"We should not be naive," he said. "We will not change the situation here overnight."