BY ALFONSO CHARDY AND JAY WEAVER

One of the first things the businessman noticed about Luis Posada Carriles was that he spoke funny. Posada, who mumbled because of an old bullet wound in his jaw, frequently visited the businessman's Guatemala utility company in 1997 to meet with two co-workers.

The businessman grew suspicious after one of the workers told him about Cuban exile plans to assassinate Fidel Castro and after a Venezuelan politician confided that Posada, a CIA-trained explosives expert, was a ``very dangerous individual.''

Concerned that Posada was using his utility business to plot illicit activities, the businessman hid a transmitter in an office and overheard the two co-workers talk with Posada about placing a ''putty-like explosive'' in the shoes of Central Americans paid to pose as tourists on trips to Cuba.

Soon afterward, the businessman became a ''confidential source'' for the FBI's investigation into bombs that exploded at Cuban tourist sites in 1997, killing an Italian and wounding seven others.

The businessman, a Cuban-American engineer who set up the utility company in Guatemala City in 1996, could turn out to be the central figure in the Justice Department's rekindled criminal investigation of Posada. The probe is back on track -- despite the fact that the FBI field office in Miami destroyed evidence in 2003 about the initial Cuba bombing case.

Federal grand juries in New Jersey and Texas are investigating the secret activities of Posada, 78, who is detained at an immigration facility in El Paso, Texas. The Texas probe focuses on whether he lied about how he sneaked into the country. The New Jersey investigation, aided by the FBI in Miami, is zeroing in on his role as the alleged mastermind of the dozen tourist-site bombings in Cuba that investigators think were financed by Cuban exiles in Union City, N.J.

Either of the probes could lead to the first indictment of Posada in the United States.

An insight into the Justice Department's case can be found in a 10-page affidavit obtained by The Miami Herald. In the June 10, 2005, sworn statement, FBI special agent Thomas H. Rice portrayed Posada as a dangerous man bent on killing Castro and spreading terror on the communist-run island to destroy its tourism economy.

''The FBI is unable to rule out the possibility that Posada poses a threat to the national security of the United States,'' Rice wrote.

Among the evidence cited in the sworn statement:

• In late August 1997, the businessman at the Guatemala utility company said he and a co-worker discovered ''what appeared to be explosive materials'' in the firm's office, where Posada regularly met with two other workers.

The businessman later told the FBI that the materials consisted of 22 transparent plastic tubes filled with a tan substance. They were labeled with the name of the manufacturer and ``explosivos de alto poder, extremadamente peligrosos'' -- high-power explosives, extremely dangerous.

• The businessman said he found funnels in the office that he thought were used to mix explosive materials with liquid inside shampoo bottles. He also found a diaper that may have been used to absorb the liquid in the bottles and yield the explosives.

The businessman then found a carrying case containing a note in Spanish, which said, ''The tyrant has to be eliminated, regardless of how many others are killed.'' Also found in the case: a note pad with Posada's name written on the first page.

• During the FBI's investigation of the 1997 Cuba bombings, agents collected records showing about $19,000 in wire transfers from the United States to ''Ramon Medina,'' one of Posada's aliases, in El Salvador and Guatemala between Oct. 30, 1996, and Jan. 14, 1998.

The FBI agent specifically refers to an Aug. 25, 1997, fax intercepted by the businessman's co-worker at the Guatemala utility company.

The cryptic fax is signed Solo. Investigators think Posada sent the fax from El Salvador to the utility company, addressed to two alleged co-conspirators who worked there.

Handwritten in Spanish, it refers to Western Union wire money transfers totaling $3,200 from four men in Union City to pay a ``hotel bill.''

It also alludes to some previous discussion Solo had about the need for publicity for certain actions. But there is no mention of Posada or bombings.

''As I explained to you, if there is no publicity, the work is useless,'' Solo wrote, adding: ``The American newspapers don't publish anything that hasn't been confirmed. I need all the information regarding the discotheque in order to try to confirm it. If there is no publicity, there will be no payment. I'll be awaiting news today, tomorrow I'll be leaving for two days.''

Since the fax became public in 1998, after it was reported first in The Miami Herald and then in The New York Times, it has come to be seen as a crucial document in the current investigation. It was included in the hundreds of pages turned over May 19 to the El Paso court considering Posada's custody.

In New Jersey, three of the people mentioned in the fax -- Abel Hernández, Rubén Gonzalo and his son, José -- have been approached by FBI agents and subpoenaed by the federal grand jury in Newark. Authorities wanted to know whether they helped finance the Cuba bombings.

Attorney Gilberto Garcia, who represents the three men and two other Cuban exiles also subpoenaed by the grand jury, said none had any role in the bombings.

''My clients had no knowledge about the financing of the bombings,'' Garcia said. ``They had no participation.''

Nevertheless, Garcia said two of the five refused to testify and invoked their right against self-incrimination -- then prosecutors excused them. Two others agreed to provide information to prosecutors, and one actually testified before the grand jury. Those three said they had not been involved in the bombings.

Garcia said his clients' names on the Solo fax were ``misappropriated.''

''Someone was sending these money transfers to Guatemala using their names,'' he said.

Although Posada was suspected as the mastermind of the bombings, he was never charged in the initial probe, largely because federal investigators insist that the Cuban government failed to help them build a case against him. But the federal case was reactivated after Posada, a Cuban-born Venezuelan citizen, sneaked into the United States last year.

The U.S. attorney's offices in Newark and El Paso declined to comment.

Eduardo Soto, Posada's attorney, said his client has not received a so-called target letter from federal authorities alleging that he is a suspect in a crime. Soto said his client did not lie about his entry into the country and was not involved in the Cuba bombings.

In El Paso, three Cuban exiles from Miami -- José Pujol, Rubén López Castro and Ernesto Abreu -- have refused to testify, and at least two of them, Pujol and López Castro, are facing prosecution.

The current Newark investigation has gained momentum as the FBI pieces together evidence -- including the fax allegedly sent by Posada listing suspected U.S. co-conspirators involved in the financing of the bombing campaign.

The government has stepped up its effort to keep Posada in detention because the federal judge in El Paso has set a Feb. 1 deadline for the Justice Department to demonstrate why he shouldn't be released in the United States, since he cannot be deported.

The reason: No country has offered to take him. Also, an immigration judge has ordered that he not be sent back to Cuba or Venezuela.

Castro and Venezuelan President Hugo Chávez accuse Posada of masterminding the 1976 bombing attack that brought down a Cuban airliner, killing 73 people.

Both leaders have used Posada as a propaganda weapon against the United States, which was embarrassed by his illegal entry into the country in the post-9/11 climate when anti-terrorism defenses were supposed to be tighter. Castro and Chávez have accused federal officials of coddling a ``terrorist.''

For his part, Posada has blamed Cuban agents for a 1990 assassination attempt in which he was shot through the jaw and chest in Guatemala.

The Justice Department's renewed Cuba bombing probe was challenging at first because the FBI had destroyed some documents, such as Western Union cables and other case records, in the fall of 2003 -- after obtaining approval from the U.S. attorney's office in Miami.

In the initial case, the Cuban government was cooperative with federal authorities. A team of FBI agents visited Cuban counterintelligence officials on the island in June 1998. The Castro government said it shared information on the tourist bombing attacks and other alleged Cuban exile terrorism activities during the 1990s.

But ultimately, Cuban officials refused to allow FBI agents to talk with witnesses or suspects or to conduct forensic examinations of explosive materials recovered from the tourist-site bombings, according to federal authorities.

The final breakdown came in September 1998, when a federal grand jury in Miami indicted 10 Cuban agents on charges of infiltrating South Florida to spy on the U.S. government and the Cuban-American community.

One of the key pieces of evidence in the current Cuba bombing investigation is the mysterious fax signed Solo.

The link between Posada and the fax was reported first in The Miami Herald on June 7, 1998. A New York Times article the following month said a Cuban-American businessman in Central America, Jorge ''Tony'' Alvarez, had discovered the fax in his office. Alvarez claimed it had been sent by Posada from El Salvador.

The article also asserted that Posada acknowledged being the author of the fax, and an accompanying story quoted Posada as saying he was responsible for the bomb attacks at Cuban tourist sites, including the one that killed the Italian.

''We didn't want to hurt anybody,'' the story quoted Posada as saying. ``We just wanted to make a big scandal so that the tourists don't come anymore. We don't want any more foreign investment.''

According to the story, Posada added: ``It's sad that someone is dead. But we can't stop. That Italian was sitting in the wrong place at the wrong time.''

For investigators, Posada's statements amounted to a confession.

Last year, prosecutors from the U.S. attorney's office in Miami sent subpoenas to The New York Times and freelance writer Ann Louise Bardach, demanding the recordings and any other documents she might have that were connected to the interview. Lawyers sought to quash the subpoenas, and the government withdrew them.

In October, the grand jury in Newark issued a new subpoena to Bardach. She said her Miami lawyer is preparing a response to quash it.

Taken together, the fax, FBI witnesses and the tapes could be crucial pieces of evidence in any effort to indict Posada.

In testimony to an immigration court in El Paso last year, Posada acknowledged that he had made those statements to Bardach -- but noted that he did not understand her questions and did not provide proper answers because his English was poor.

In the end, the Cuban government arrested several of the bombers.

And over the next decade, the tourism industry was far from disrupted. Travel to Cuba became all the more popular, with the total number of visitors doubling to more than two million last year.