BOGOTA — A semi-submersible ship, ready to be loaded with six tons of cocaine, was seized by Colombian military near the northern coast of the South American nation, the Navy reported Monday.

The watercraft, roughly 66 feet (20 meters) long, was kept in a workshop, part of a four-building complex that included housing for some 25 people, a cellar and cooking facilities, according to the naval report.

When troops arrived at the complex, they were hit by gunfire, while unidentified individuals set fire to the craft and fled, they reported.

The Navy has attributed ownership of the craft to drug trafficking gang Los Urabenos and the militant rebels of the Revolutionary Armed Forces of Colombia (FARC), in what it calls "a criminal alliance to sell drugs on the international black market."

The watercraft is the fifth semi-submersible to be seized this year and the 76th to be seized since 1993.