GUATEMALA CITY (AP) _ U.S. and Guatemalan authorities announced Wednesday they seized more than 2 1/2 tons of cocaine from a boat in a Caribbean port in one of the largest drug busts on record.

Six Americans, a Canadian and a Guatemalan were arrested in the raid Monday on the boat, the Daring, in Puerto Barrios, 150 miles northeast of Guatemala City, a U.S. Embassy communique and Guatemalan authorities said.

The eight were being held in the Puerto Barrios jail under special guard, with security reinforced by the Guatemalan army and a Guatemalan air force helicopter, national prison director Cesar Rivera Claverie told reporters.

The embassy communique said the 5,236 pounds of cocaine have a retail value in the United States of $500 million.

Embassy spokesman John Treacy said it was the fifth largest seizure in the world in which U.S. federal agents had been involved. He could not say what the other four were.

The communique said the cocaine entered Guatemala on Saturday and Sunday on two airplanes that arrived from Colombia and landed near Lake Izabal, 42 miles southwest of Puerto Barrios and 108 miles northeast of Guatemala City.

''The cocaine was transferred to the Daring, of Panamanian registry ... It is believed that the destination of the cocaine was Florida.''

The operation followed more than a year of investigation and was a joint effort by the Guatemalan security forces and the U.S. Drug Enforcement Agency, the embassy said.

''Other arrests are expected in the United States as the investigation continues,'' the statement said.

The embassy said the 175-foot boat was equipped with radios and radar. While the embassy said it was registered in Panama, Guatemalan authorities said they were trying to confirm this.

Rivera Claverie identified those arrested as Joseph La Chapelle, 62, of Rhode Island; Robert Henry Harvey, 50, of West Virginia; Willand Griffin Hughes, 64, of West Virginia; David Anthony Miller, 40, of West Virginia; Edward Eugene Stone Jr., 47, Tennessee; Regis Allen, 41, of Pennsylvania; Jean-Yves Gustave Ovide Fillion, 64, Quebec, Canada; and Fernando Toriello Aramburu, 27, of Guatemala.

Puerto Barrios Judge Gustavo Gaitan confirmed the names and said they were being held on charges of illegal trafficking of drugs, which carries a penalty of three to six years in jail.

Their hometowns were not available.

The United States will seek extradition, the communique said.