BY ALFONSO CHARDY

 Federal investigators have reopened the case of Eriberto Mederos and are looking for witnesses or documents to verify allegations that the former orderly at Havana's psychiatric hospital tortured political prisoners with electroshock treatment, according to U.S. Justice Department sources familiar with the case.

 The sources said investigators are looking for new evidence as a first step toward convincing senior immigration officials to reopen the Mederos file and, possibly, strip him of his U.S. citizenship.

 Lack of corroborating witnesses and documentation, the sources said, was among the factors when the U.S. Immigration and Naturalization Service in 1993 granted U.S. citizenship to Mederos despite being aware that several former prisoners held at the hospital alleged he had given them electroshock as punishment or in connection with interrogation sessions.

 Those allegations first surfaced in a book published in 1991. They were repeated in front-page newspaper stories nationwide in 1992.

 Despite that, the INS in May 1993 naturalized Mederos when investigators concluded they could not challenge his contention that electroshock treatment was a medical procedure -- not torture, the sources said.

 Patricia Mancha, an INS spokeswoman in Miami, declined comment on the case, citing ``privacy issues.''

 HUMAN RIGHTS GROUP

 The Mederos case is once again in the headlines as a result of pressure from a human rights organization in Boynton Beach that wants the U.S. government to detain and deport foreign nationals accused of having tortured or killed political foes.

 The group, International Educational Missions, has specifically asked the INS to begin proceedings to strip Mederos of his U.S. citizenship.

 But INS officials, not referring specifically to Mederos, said that before they can strip a naturalized American of citizenship, the agency needs witnesses who can prove that the person lied to obtain citizenship.

 ``If any individual has information relevant to someone acquiring naturalization through fraudulent means, we welcome them to come forward and supply this information to us,'' an INS official said. ``There is a burden of proof which the government must adhere to, and we take every allegation seriously and investigate it.''

 Mederos, who lives in the Allapattah neighborhood of Miami, north of downtown, declined two requests for an interview. But in the past, Mederos has insisted that the electroshock treatment he delivered was ordered by doctors.

 Richard Krieger, head of International Educational Missions, said he was writing a letter to U.S. Attorney General John Ashcroft requesting that the INS reopen the
 Mederos file with a view to stripping him of citizenship.

 Under U.S. law, denaturalization proceedings can begin if investigators obtain ``credible and probative evidence'' to establish that a naturalized individual concealed "a material fact'' from his or her background when applying for citizenship.

 The INS application for naturalization specifically asks: "Have you at any time, anywhere, ever ordered, incited, assisted or otherwise participated in the persecution of any person because of race, religion, national origin or political opinion?''

 If Mederos answered no, then law enforcement officials need to find witnesses to verify allegations he used electroshock as torture -- not as a medical procedure as he has insisted all along.

 Mederos insists that the electroshock treatment was a legitimate procedure given on doctors' orders.

 "These are accusations from people looking for publicity,'' Mederos told El Nuevo Herald in an interview published April 16, 1992. ``It's my word against theirs. I say that their treatments are recorded in their medical files in Havana. They say the opposite.''

 Public records list Eriberto Mederos at two different addresses -- one in the western part of Miami-Dade County near the junction of the Homestead Extension of Florida's Turnpike and State Road 836, and the second in Allapattah between State Roads 836 and 112 just east of Miami International Airport.

 Mederos' daughter, Vivian, told The Herald last month that her father had moved out of the West Miami-Dade address five or six months earlier and that she did not know his new address.

 'NOVEL HAS ENDED'

 The Allapattah address is at a small, one-story pink duplex apartment. One morning late last month, a man emerged from the apartment. Asked if he was Mederos, the man said: "Yes, that's me.''

 Told that The Herald was preparing an article on him, Mederos smiled and said: "This is a novel that has ended.''

 Mederos added that he gave interviews in 1992 when his Havana work was revealed and he planned no more.

 ``Thanks for your interest, though,'' Mederos said as he got into his car and drove off.

 The world first learned about Mederos in 1991 when authors Charles J. Brown of Freedom House and Armando M. Lago of Of Human Rights published The Politics of Psychiatry in Revolutionary Cuba.

 After being discovered in 1992 working at a Hialeah convalescent home, Mederos acknowledged delivering electroshock treatment -- but categorically denied it was torture.

 Mederos began working at the Havana hospital in 1945 when he was 22 and left in 1980 when he was 57, according to published reports in the 1990s.

 In 1984, Mederos arrived in Miami. It's unclear if he came as a refugee, immigrant or visitor who then stayed or asked for political asylum.

 In 1990, a former inmate at the Havana hospital recognized Mederos walking on a Hialeah street one morning.

 "I saw Mederos leaving a restaurant,'' said José Ros, who alleged that Mederos tortured him with electroshock at the psychiatric hospital in the 1970s. "As soon as I saw him, I felt like an electrical current went through my body. I turned around and went back to try to talk to him but by then I couldn't find him.''

 Herald staff researcher Elisabeth Donovan and El Nuevo Herald staff writer Pablo Alfonso contributed to this report.