MIAMI-A Florida International University professor and his wife, an FIU counselor, were accused Monday of operating as covert agents for Cuba’s communist government for decades, using short-wave radios, numerical-code language and computer-encrypted files to send information about Miami’s exile community to top Castro intelligence commanders.

U.S. Magistrate Judge Andrea Simonton expressed such dismay over the alleged espionage-related history of Carlos M. Alvarez, 61, and his wife, Elsa Alvarez, 55, that she denied them bond before trial on a charge of failing to register with the federal government as foreign agents.

Simonton said she believed that the gravity of the charges admitted by the couple this summer to the FBI, their past academic trips to Cuba and their contacts in Fidel Castro’s government made them a flight risk if allowed to return to their South Miami home.

“As a practical matter, these are people who admitted they were spying,” Simonton said. “They would indeed return to Cuba, rather than face the consequences of their actions here.”

The indictment, which included no mention of top-secret U.S. government information being disclosed, came months after the couple’s confessions because of additional investigative work in the case, interim U.S. Attorney R. Alexander Acosta said.

The case of the longtime FIU employees marks the biggest Miami spy-related case since 1998, when five men were charged with infiltrating the exile community and laying the groundwork for the shootdown of four Brothers to the Rescue pilots by the Cuban Air Force two years earlier.

If convicted of one count of not registering as foreign agents, the Alvarezes could face prison sentences of seven to 10 years. An arraignment is set for Jan. 19. They are being detained at the Miami Federal Detention Center.

FBI agents arrested Alvarez and his wife on Jan. 6 at their home, valued at about $750,000, which they had hoped to use for bond. An indictment, returned in late December, was unsealed at their two-hour court hearing on Jan. 9, which was attended by the couple’s four adult children, FIU President Mitch Maidique, a Catholic priest close to the defendants and numerous reporters.

According to an FBI agent and federal prosecutors, the couple transmitted information about Miami’s exile community including leading groups such as the Cuban American National Foundation and Brothers to the Rescue. They did not send any military or classified information, but they did provide Cuban officials with the identity of an FBI employee who had once been an FIU student of Carlos Alvarez.

Carlos Alvarez is an associate professor of educational leadership and policy studies at FIU who also does psychological screenings of police cadets for the city of Miami and Miami-Dade County police departments.

Elsa Alvarez is a psychological counselor at FIU.

“They used their academic positions as covert covers to spy for the Cuban government,” said Assistant U.S. Attorney Brian Frazier. “They were living a lie.”

Frazier said Carlos Alvarez had spied for Cuba since 1977 and Elsa Alvarez since 1982. He said that Elsa, Carlos Alvarez’s second wife, had been independently spying for the Cuban government before she teamed up with her husband.

It was unclear what motivated the couple to act as alleged spies for so many years. They were not paid for the information they gathered, though Cuba covered their expenses such as travel, lodging and meals, authorities said.

Thanks to a tip, the FBI had been monitoring the couple-Carlos Alvarez used the alias “David” and his wife used “Deborah”-for months before each gave separate confessions in June and July to agents about their alleged spying activities. The Naval Criminal Investigative Service assisted the FBI.

Frazier said they admitted to using high- and low-tech methods to communicate with Cuba’s Directorate of Intelligence and several of its “handlers.”

Among them: an antenna in their backyard, a short-wave radio, five-digit code, encrypted computer disks and local post office boxes.

Since the early 1990s, the couple traveled to Cuba several times on U.S.-authorized educational trips, bringing along FIU students, Frazier said. He called the trips a “pretext to do other things.”

The couple also shared information with Cuban intelligence agents in Mexico, South America and the United States, Frazier said.

Frazier said the couple was so good at their work the Cuban government gave them commendations in the 1990s.

But attorney Steve Chaykin, representing Carlos Alvarez, and lawyer Norman Moscowitz, representing Elsa Alvarez, said their clients had strong ties to their family and community. They stressed they did not leave the country after they admitted to their alleged espionage work for the Cuban government this summer.

“There is not a scintilla of evidence … that they contemplated leaving” for Cuba, Moscowitz said, noting that his client is in poor health and has to take care of her 12-year-old daughter and elderly parents.

Chaykin said neither gave information to Castro intelligence officials that “in any way endangers the U.S. government or military.”

Simonton, the magistrate judge, was not persuaded.

The couple’s arrests came as a federal appellate court in Atlanta plans to hear arguments next month in an unrelated Cuban spy case in which five men were convicted of espionage charges.

The entire 11th U.S. Circuit Court of Appeals will determine whether pretrial publicity in that case tainted the jury pool.

Last October, the appellate court threw out an earlier ruling by a three-judge panel that had overturned the 2001 convictions for the so-called Cuban Five on espionage charges. The decision pleased relatives of four Miami exile pilots who were fatally shot down over international waters in 1996 by the Cuban Air Force in an alleged plot linked to the espionage case.