A letter from a Cuban secret police agent to "Samuel," a Cuban spy working in Miami, was found in the briefcase of Salvador Aldereguia-Ors when he was arrested at Miami International Airport last week, The Herald learned Tuesday.

The FBI is investigating the possibility that Alderguia is "Samuel."

Aldereguia and his former boss, Cuban exile banker Guillermo Hernandez-Cartaya, the chief executive officer of WFC Corp. of Coral Gables, were bound over to a federal grand jury Tuesday on passport violation charges.

But even as an FBI agent testified about the alleged passport violations, the still secret contents of Alderguia’s briefcase became the subject of intense interest.

"I Gained the impression that it had something to do with national security," Special Agent Morris W. Haddock of the FBI said Tuesday when asked about the briefcase’s contents.

Haddock said he had not personally seen the contents, but had discussed the documents found in the briefcase with another FBI agent who had reviewed them in detail.

Haddock did not testify about the letter to "Samuel," but sources close to the investigation confirmed that the letter was found in the briefcase.

Alderguia, who was arrested March 3 while attempting to board an Air Jamaica jet bound for Kingston, Jamaica, testified at an earlier hearing that he intended to meet with Cuban Consular officials there. He said the meetings were related to an effort to bring refugees out of Cuba to the United States.

However, the letter found in his briefcase has caused investigators to doubt his explanation.

Investigators said the letter directed "Samuel" to return to Cuba. Investigators speculate that Alderguia was headed for the Cuban consulate in Jamaica to protest the reassignment.

FBI agents arrested him only minutes before he would have left the country, perhaps for good.

Alderguia and Hernandez-Cartaya were charged with conspiring to use a fraudulent passport in July. But sources said the passport charge may have been simply a means of keeping Alderguia in the country.

The alleged violations centered on a fake passport which Aldereguia is accused of preparing for Hernandez-Cartaya.

The passport, issued by the State Department to Aldereguia in June 1977, was altered to make it appear to belong to Hernandez-Cartaya . His photograph was pasted in it, and a corporate seal was used to replace the U.S. seal on the photo, according to FBI testimony.

Similar photographs of Hernandez-Cartaya were found in Aldereguia’s briefcase when he was arrested, along with Aldereguia’s own passport and the letter to the agent called Samuel.

Special Agent Willis Walton of the FBI testified last week in his only appearance in court, that the briefcase also contained "operational instructions from a foreign country," directives for activities in the United States, and other papers.

An FBI affidavit filed last week on which the passport charges were based cited two confidential informants, identified only as "source one" and "source two."

Source one, The Herald has learned, is attorney David E. Masnata, Jr., a former officer of WFC Group Inc., an affiliate of the world-wide WFC banking empire. Masnatat sued Hernandez-Cartaya in Circuit Court last year when their relationship soured.

Masnata took the passport allegedly forged by Aldereguia to London, where he was to deliver it to Jose Sarria, who represented WFC interests in England. Sarria was to take the passport to the Arab state of Ajman, where Hernandez-Cartaya was waiting. Local authorities had seized his passport over a business dispute involving the Ajman Arab Bank, in which WFC had a 20 per cent interest. The bank had invested $37 million, some of it borrowed from Swiss banks, in WFC projects in the United States, according to the FBI affidavit.

Tuesday Haddock testified that Masnata, whom he identified only as "source one," never gave Sarria the passport because he feared it might be illegal. Masnata later turned it over to the FBI.

Source two, The Herald has learned, was Fernando Capablanca, a former WFC officer, who was present at a WFC board meeting June 10 or 11, 1977, when Masnata reported that Hernandez-Cartaya was unable to leave the Arab country.

Masnata told the FBI that Aldereguia told him he had given up his own passport to help his "fat friend in Ajman." He said Aldereguia told him he "had been unable to do a good job on changing the passport" on such a short notice.

Neither Hernandez-Cartaya, Aldereguia, Capablanca nor Masnata could be reached for comment.