BOGOTA - The Colombian navy seized 12 tons of cocaine on Monday on a container ship in the port of Cartagena that was due to sail to Veracruz, Mexico, authorities said.

Sniffer dogs discovered the drugs, hidden in containers loaded with molasses paste, said Admiral Roberto Garcia, chief of operations of the Colombian Navy.

He told reporters the cocaine was from the Valle del Cauca region in southwest Colombia, where former right-wing paramilitaries have formed gangs that have taken over the narcotics trade once run by powerful cartels.

Related readings:  DPRK detains 2 Japanese in drug probe  Drug kingpin captured in Colombia-US joint operation  Russia makes little progress against drugs  Australian police smash drug ring

Anti-drug police said the Cartagena haul - with an estimated value of $360 million - was one of Colombia's biggest seizures in recent years. In 2008, 10.5 tons of cocaine were found in the neighboring Caribbean port of Barranquilla.

The Andean nation is the world's largest producer of cocaine, which is mainly smuggled to the US market through Latin American nations such as Mexico, where brutal cartels control the trafficking routes.

Over the last decade, the United States has poured $5 billion dollars into Colombia to fight drugs with military equipment and crop eradication programs.

Colombian cocaine output dropped 19.5 percent last year - to 279 tons - due to heavy rains, crop eradication and military enforcement, according to official estimates.

But cocaine continues to flow north in large quantities in a multibillion-dollar business that funds Colombia's left-wing guerrillas and increasingly former paramilitary groups.

Cash continues to move south.

A Mexican man was caught at Bogota airport after arriving from Mexico with $2.8 million in US bills in his luggage, Colombian customs police said on Monday. They suspect the cash was payment for Colombian drugs shipped to the Sinaloa cartel.