MIAMI (CNN) -- Ten people were set to be arraigned at a federal court
                  in Miami Monday afternoon, charged with spying for the Cuban
                  government.

                  The eight men and two women were arrested without incident Saturday in
                  the Miami area, following a four-year investigation by the FBI. They face
                  charges including espionage, and failure to register as agents of another
                  nation.

                  Congressional sources said the arrests were timed to avert an operation
                  planned by the suspects, but provided no details. It was not immediately
                  clear whether they were Cuban exiles, agents who slipped into the United
                  States from Cuba, or some of each.

                  Among those accused is Rene Gonzalez, formerly affiliated with the
                  Miami-based Cuban exile group Brothers to the Rescue, which flies
                  search-and-rescue missions for Cubans fleeing their homeland who are
                  found in waters north of Cuba. He has been linked more recently to Ramon
                  Saul Sanchez's Democracia movement, which sails from the Florida Keys to
                  areas near Havana to protest Cuban government actions.

                  According to Jose Cardenas, spokesman for the Cuban American National
                  Foundation in Washington, the accused spies had infiltrated Cuban exile
                  groups, including Brothers.

                  Soon after the February 1996 shootdown of two Brothers planes over
                  international waters in which four people were killed, federal officials looked
                  into whether spies played any part in the shooting.

                  Juan Pablo Roque, a former Cuban air force pilot and double agent,
                  infiltrated the Brothers group before returning to Cuba. He said he passed
                  information about Brothers to the Cuban government.

                  U.S. Rep. Ileana Ros-Lehtinen, a Cuban-born Miami Republican, wrote the
                  FBI in June requesting a briefing by the agency's counterintelligence section
                  on two types of activities by Cuban officials in the United States.

                  She said she was concerned about "a significant increase" in travel by Cuban
                  officials to Florida and New York for private meetings and an "inordinate
                  number of meetings that Cuban government officials have been holding with
                  major U.S. corporations and industry giants."

                  FBI director Louis Freeh called Ros-Lehtinen at her home on Saturday to
                  inform her of the arrests, said her spokesman Juan Cortinas.

                            The Associated Press contributed to this report.