A Florida college professor and his wife, a university administrator, face charges that they acted as covert agents for Cuba’s communist regime for more than two decades.

In an indictment unsealed yesterday, prosecutors charged Carlos Alvarez, 61, an associate professor of educational leadership at Florida International University, and Elsa Alvarez, 55, a coordinator for the school’s counseling program, with secretly gathering information on anti-Castro efforts in South Florida. The indictment alleges that the couple served as operatives for Cuba’s Directorate of Intelligence and that Mr. Alvarez began working for the Cuban regime in 1977 or earlier.

At a court hearing in Miami yesterday afternoon, a federal magistrate, Andrea Simonton, ordered the couple held without bail.

“These were highly placed and very well-regarded operatives in the United States,” a prosecutor, Brian Frazier, said, according to the Associated Press. Mr. Frazier said the couple used an encrypted shortwave radio system to keep in contact with their Cuban handlers, the news agency said.

The U.S. attorney in Miami, Alexander Acosta, told reporters that both Alvarezes confessed to their contacts with the Cuban government after being confronted by investigators this summer.

“Carlos Alvarez further abused our trust and betrayed our community by coordinating and leading a student exchange program to Cuba, where the opportunity to further manipulate and indoctrinate students was possible,” Mr. Acosta said, according to a local television station, WFOR-TV.

Attorneys for the Alvarezes asked that the couple, who have five children in America, be released on bond, news reports said. No pleas were entered yesterday. If convicted, each defendant faces up to 10 years in prison and a fine of up to $250,000.

Officials at Florida International University did not return calls seeking comment yesterday, but a former colleague of Mr. Alvarez said he was taken aback by the allegations.

“I’m stunned and at this point not believing,” professor Michael Parsons, told The New York Sun yesterday. “It’s not so much a case of not believing Carlos did what he said he did but that the government now thinks he’s a spy.”

Mr. Parsons, who headed the educational leadership and policy studies office at Florida International until last year, said Mr. Alvarez was active in seeking rapprochement between the Cuban and Cuban-American communities. He was open with colleagues about his work, but did not publicize it in Miami, Mr. Parsons said. “It’s a crazy environment,” he said.

Mr. Parsons, who recently moved to a Minnesota university, said he did not believe Mr. Alvarez was a spy. However, the former colleague appeared to be at a loss when asked about the claim that the couple had encrypted radio equipment. “I can’t explain that,” Mr. Parsons said.

Mr. Alvarez also was affiliated with a conflict resolution program at Harvard’s Weatherhead Center for International Affairs. According to records posted on the Internet, he lectured at Harvard’s faculty club in November 2002. The professor who granted the affiliation to Mr. Alvarez, Herbert Kelman, expressed surprise at the latest developments.

“It’s a great shock and surprise to me. I would never have anticipated that,” Mr. Kelman told the Sun yesterday. “I have the highest regard for him.”

Mr. Kelman, who is now a professor emeritus, said he met Mr. Alvarez through an international organization for social psychologists. The Harvard professor said he traveled with Mr. Alvarez to Cuba in about 1996 and observed his efforts to organize discussions between Cuban and Cuban-American students.

Mr. Kelman said he saw no indication that Mr. Alvarez had unusual entree with Cuban officials. Instead, the Florida professor seemed frustrated with getting Cuban approvals for his programs. Mr. Kelman said he recalled talking with Mr. Alvarez about the difficulties in dealing with the Communist Party officials that permeate universities in Cuba. “He had, as far as I know, the same reservations about this way of operating as I did,” Mr. Kelman said.

A Cuban-American academic at the University of Miami, Andy Gomez, said he met Mr. Alvarez on a few occasions, but did not know him well. “I know who he is. It’s a small circle of Cuban-American and Cuban professors here in South Florida,” Mr. Gomez, whose work focuses on planning for the post-Castro era, said.

Mr. Gomez said it was premature to reach conclusions about the charges against the Alvarezes, but there is no question that the Castro regime is active in America. “We know for a fact that the Cuban government has had people placed in here in Miami to follow various communities, including people involved in the Cuban transition,” he said. “They’re very much involved in the spying game not only here in South Florida, but throughout the United States.”

In August, a federal appeals court overturned the sentences of five men who were convicted on charges of being agents of the Cuban government. The three-judge panel said pervasive anti-Castro sentiment in southern Florida prevented the five from getting a fair trial. However, that ruling was set aside when the full bench of the 11th Circuit Court of Appeals agreed to examine the case. Lawyers are expected to argue the case again next month.

In 2002, an analyst at the Defense Intelligence Agency, Ana Montes, confessed to spying for Cuba for 17 years. She was sentenced to 25 years in prison. The following year, more than two dozen Cuban diplomats were expelled from America on suspicion of espionage.

In charging the Florida couple with failing to register as foreign agents, but not with outright espionage, prosecutors used a technique favored increasingly by the Justice Department. Similar charges have been leveled in cases involving alleged agents for China, the Philippines and Saddam Hussein’s former regime in Iraq. The failure-to-register charges do not require that the government show that national security secrets were lost or that the defendants knew their actions could harm America.