The occupants of the boat fled into the jungle, and law officers confiscated 775 kilos of cocaine.
The boat was of the go-fast type with three 2200-horsepower motors on the stern.
The crew engaged the pursuing coast guard vessel in a fire fight, but there were no reports of injuries to law officers. Typically Costa Rican patrol boats do not carry mounted guns.
The action began about three nautical miles off the mouth of the Río Jaloba. That location is close to the border with Nicaragua.
The Servicio de Vigilancia Aérea was patrolling the air above the scene as night fell in an effort to find the fugitives. Patrolmen were on foot. Officers of the Policía de Control de Drogas also were looking for sacks of drugs that may have been dumped overboard.
The go-fast boat appears to have evaded detection for much of its trip up the Costa Rican coast. Frequently these nighttime drug trips are spotted by U.S. boats whose crews then notify Costa Rican law officers.