SAN JUAN, Puerto Rico (AP) _ Customs agents arrested three American soldiers and a Panamanian after finding 77 pounds of cocaine in the U.S. military plane in which they had flown from Panama, an official said Wednesday.

The four, wearing U.S. Army uniforms, were detained at Roosevelt Roads Naval Station after the cocaine was discovered during a routine customs check Saturday, said Mamie Pollock, U.S. Customs Service regional director.

The men arrived in Puerto Rico on a Military Airlift Command flight that originated in Howard Air Force Base in Panama, said Ensign Javier Irizarry, public affairs officer at the Roosevelt Roads base.

A Nebraska man was charged Monday with smuggling cocaine into the United States on a flight from the same base in Panama. The American, Bruce H. Davenport, 33, of Omaha, Neb. was accused of carrying the cocaine on a U.S. general's plane.

There was no indication whether the two cases were related.

Federal grand juries in Miami and Tampa, Fla. have been hearing testimony about possible links between Panama's strongman, Gen. Manuel Noriega, and drug trafficking. Noriega has denied any role in drug smuggling.

The Drug Enforcement Administration identified the four men arrested in Puerto Rico as Rafael A. Valladares, a Panamanian; and Darryl Taylor of Springfield, Ill., Franklyn Brown of Forest Heights, Md., and Bruce Milton Mack of Chicago. Their ages and ranks were not available.

Taylor and Brown were reported to have been stationed at Fort Clayton on the east coast of Panama and Mack at Fort Kobbe on the west coast.

The Drug Enforcement Adminstration and the U.S. Attorney's Office in Puerto Rico are conducting a probe into the case, Pollock said.

Customs agents assisted by drug-sniffing dogs seized about 77 pounds of cocaine with a wholesale value of $350,000 to $420,000, DEA Special Agent Arthur Barnes said in a telephone interview Wednesday.

A spokesman at Roosevelt Roads, on Puerto Rico's east coast, said the pilot and crew were not arrested.

''As far as we know at this time, none of the crew members were involved in this. Those arrested were passengers,'' said Irizarry.

The DEA said Taylor, Brown and Valladares were charged in sealed indictments involving cocaine possession and importation. The indictments were issued Monday by U.S. Magistrate Roberto Schmidt Monge. He denied them bail.

Mack was charged with attempting to smuggle 37 pounds of the drug into the United States.

Barnes said it is common to issue sealed indictments in cases where the possibility of further arrests are possible.

The Associated Press tried unsuccessfully to reach U.S. Attorney Daniel Lopez Romo at his office Wednesday. Reporters were told only Lopez Romo or his deputy, Charles Fitzwilliam, could comment on the case. Fitzwilliam was not available by phone.

Davenport, a Lockheed Aircraft employee, was arrested Monday after he allegedly delivered 11 pounds of cocaine and $101,000 to an undercover agent at a motel near Andrews Air Force Base.

Davenport told the agent on a flight last October from Panama to New York that he was in charge of maintenance for a U.S. general's plane at Howard Air Force Base and could smuggle small amounts of ''coffee'' into the United States, federal authorities said.

Stephen L. Purcell, an assistant U.S. attorney, refused to identify the general whose plane was allegedly used.

Davenport was charged in Camp Springs, Md.