The Colombian navy reported Tuesday that it seized a small submarine used to smuggle cocaine off the country's southwestern coast.

The semi-submersible vessel was spotted adrift last Saturday 60 nautical miles from the mouth of the Naya River by air and maritime units and authorities found that it had no cargo or crew on board.

Authorities presume that the sub - which has the capacity to carry four tons of cocaine - was going to be loaded and sailed to Central America.

The vessel is "a very appealing mechanism" for drug traffickers, thanks to its small profile above the ocean's surface, a situation that makes "its detection and neutralization more complicated," navy Capt. Carlos Delgado told Efe.

Delgado added that the two engines of the semi-submersible vessel give it a "very basic" ability to navigate, supported by the use of GPS that marks "its route from the start to the destination site, where the other part of the organization awaits it."

The sub is approximately 15 meters (49 feet) long, 3 meters (10 feet) wide and can carry a crew of four, and it is the first vessel of its type found by authorities this year, although the Colombian navy seized eight similar subs in 2012.

"It's a mechanism that is still in use and is being used more," Delgado concluded. EFE