Authorities seized two semisubmersible vessels loaded with nearly 5 tons of cocaine last weekend off the Pacific coast of Colombia, the nation’s navy announced. The “narco subs” were intercepted during a joint operation by the country’s navy and coast guard, officials said in a statement Sunday.

Authorities said the two vessels carrying 4.9 tons of cocaine toward Central America were intercepted in the South Pacific. Six suspects were arrested.

Officials released four images from the operation, including one that showed stacked packages of the alleged drugs laid out on the ground and another that appeared to show suspects surrendering on a semisubmersible.

In a statement, the Colombian navy said it would continue working “on coasts, rivers, seas and island areas” to fight drug trafficking.

Colombian authorities said that officers have now seized a total of 13 “narco subs” so far this year. The Colombian navy said it intercepted 20 semisubmersibles in all of 2023, leading to the seizure of 30 tons of cocaine and more than 5 tons of marijuana. 

Semisubmersibles lie very low on the ocean’s surface but cannot go fully underwater. They are popular among international drug traffickers because they can often elude detection by authorities. The vessels are sometimes seized in Colombian waters while heading to the United States, Central America and Europe.

In February, Colombian authorities on a search-and-rescue mission for two missing fishermen found a “narco sub” loaded with more than 4 tons of cocaine. A few weeks before that, the Colombian navy intercepted a semisubmersible loaded with more than 1,000 pounds of cocaine in the Pacific Ocean.

Last month, Italian police seized a small remote-controlled submarine they said was likely intended to transport drugs internationally.

Authorities around the globe have made other major drug busts in international waters recently. Just a few days ago, the U.S. Coast Guard said it offloaded $63 million worth of cocaine at a port in Florida after a high-speed shootout that sank a suspected drug smuggling boat and its crew in the Caribbean Sea. Last month, the French navy said it confiscated 2.4 tons of cocaine from a fishing boat in the Atlantic Ocean.