SAN JUAN, Puerto Rico — Three men were indicted Monday in a case that federal authorities say involves some $75 million worth of cocaine found aboard a semi-submersible vessel, the first time such an apparatus has been seized in Puerto Rico.

The U.S. Attorney’s Office said the suspects were transporting about 5,500 pounds (2,500 kilograms) of cocaine aboard the vessel that was intercepted nearly three weeks ago.

The drug and vessel seizure occurred near the southeast coastal town of Yabucoa.