Spanish police intercepted an apparent drug transport submarine off the coast of the northwestern region of Galicia on Sunday.

"Early this morning, an international operation was able to locate a small submarine of around 20 meters near the beach of Hio in the province of Pontevedra," Spanish authorities told Reuters news agency.

According to Spain's national law enforcement agency, the Guardia Civil, the vessel had been carrying around 3,000 kilograms (6,600 pounds) of cocaine.

However, a Guardia Civil source told Reuters that this still needed to be confirmed, as the submarine's cargo is still underwater. Spanish authorities said they will attempt to bring the submarine to the surface Monday morning.

Read more: Southern Spain: The European drugs gateway

Spanish newspaper El Pais reported two men detained on the vessel were Colombian. The paper also said the submarine was the first such "narco sub" intercepted off the coast of Europe.

Spain's EFE news agency reported that investigators said the submarine had originated in a Latin American country.

Read more: Why is Colombia's cocaine production so high?

Narco subs are used by drug traffickers to transport large amounts of cocaine, mostly coming from production centers in South America.

In September, the US coast guard captured a drug transport submarine in the Pacific Ocean off the coast of Colombia carrying more than 5 tons of cocaine.

wmr/cmk (Reuters, EFE, AP)

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