American journalist Jon Lee Anderson was walking along the streets of Lima with his Peruvian fiance last June when three men, identifying themselves as immigration police, asked to see his papers. He told them his passport was at his apartment and they asked to go there. "Fine, Anderson said, "Let's go."

Once there, Anderson said, the police rushed into his bedroom and came out with a suitcase that to his surprise contained a half kilogram of cocaine in a bag, and a gun. The police threw him on the floor, he said, and handcuffed him as his girlfriend watched in tears. They were under arrest for possession of cocaine.

Anderson, 23, is the son of a retired Foreign Service officer. Another American journalist in Peruvian capital calls him "the closest thing in Lima to an investigative reporter." Shortly before his arrest, Anderson had written an article for The Lima Times that raised the suspicion of bribe-taking by the Peruvian police during the government's much-publicized efforts to destroy thousands of acres of illegal coca crops last spring with $425,000 in U.S. aid.

The journalist, who maintains that he is innocent, said he had just returned from several Peruvian jungle towns where he was trying to trace how the paste made from coca leaves travels from Peru to Columbia and is eventually smuggled as cocaine powder to the United States.

Anderson had also made contacts among the prisoners in one of Peru's most overcrowded prisons and written articles about conditions there.

Now, from the same prison he set out to investigate, Anderson maintains that the Peruvian drug police -- or perhaps drug traffickers in connection with the police -- planted the cocaine on him to shut him up. His case drags on, with at least one inconsistency having turned up in the prosecution's presentation, and Peru's Embassy here has assured for three months now that judicial officials were looking into the matter, including charges that Anderson was tortured.

Anderson charged that he was tortured by the Peruvian Investigative Police during his interrogation: beaten, hung from a pulley, dunked in water for hours and stung with electric shocks. A medical certificate, signed by a doctor who examined him in prison, states that Anderson suffered injuries to the spine region, arms, legs and head.

Anderson is one of 40 Americans in Peru and 869 in countries around the world who are facing drug charges. Complaints about torture and the methods of investigation used by Latin American police have grown more common in the eight years that the Drug Enforcement Administration has been working with the Latin American police.

Over the years, senators and others have questioned the efficacy of the effort, charging that despite an ever-increasing multimillion-dollar budget, the agency has merely dented the drug trade and caught mostly smalltime drug dealers rather than the kingpins.

This year, DEA will spend $205 million for its operations in Central and South America. In Peru, where the DEA trains the Peruvian Investigative Police that interrogated Anderson, the agency's office has an annual operating budget of $120,000. Five DEA agents are permanently stationed there.

The State Department also subsidizes drug enforcement operations in Peru, this year contributing $1.7 million for vehicles and equipment, staffing of drug operation centers and reduction of illegal coca crops.

Families of American prisoners have complained frequently of the close association between the DEA and the Latin American police in light of the repeated of U.S. investigation where aid is involved.

DEA officials deny any knowledge of the alleged tortures. One called the Peruvian police "one of the best, if not the best law enforcement agency in South America," DEA officials maintain that they do not participate in the Peruvian investigators, Rather, they insist that their role is strictly to train the police and exchange information on suspects.

Anderson's charges that he was tortured are the latest in a series of complaints that American prisoners have made against the Peruvian Investigative Police. The State Department now has on file 16 complaints of torture. In nine of those cases, the mistreatments were confirmed following an investigation by Peruvian officials.

In those cases, the State Department has lodged protests with the Peruvian government. That is all State says it can do. The only other assistance State gives the prisoners is to provide them with a list of lawyers and bring them vitamins twice a month.

In the Anderson case, they have taken a hands-off stand, stressing that Anderson signed a confession stating he knew there was cocaine in the suitcase, but that it did not belong to him. Anderson has said he signed this confession only after the police threatened to torture his fiance. She was freed without charge after he signed.

The State Department also said Anderson did not tell an embassy consular officer that he was tortured until a month after his arrest and still has not supplied enough details to lodge a protest.

Anderson has been held since June in Lorigancho Prison, a massive tan brick structure outside of Lima. In an interview there last August, he described coming to Peru in 1978 as a teacher aboard a ship that brought American students to tour the country. He soon became interested in writing about this land, once the seat of the highly advianced Incan culture.