The Coast Guard seized more than one ton of cocaine, worth an estimated $66 million, from a fishing boat that had been stopped off the coast of Panama, officials said Thursday.

Four Colombian nationals aboard the boat were arrested. Officials said the four were being turned over to U.S. Immigration and Customs Enforcement agents and criminal charges were likely.

The cocaine was found aboard the 40-foot fishing boat on Feb. 6 after it was stopped by a Navy frigate in international waters. The U.S. has treaties with most Latin American countries allowing it to board and search vessels operating under their flags. It was not immediately clear if the boat was bound for the United States.

The boat's master initially claimed to have 300 pounds of fish on board but then said those had been discarded, according to the Coast Guard. There were no fishing poles or lines aboard.

The cocaine was found behind a bulkhead that had been freshly painted, authorities said. It was being taken Thursday to the Coast Guard station at Miami Beach.