Superstars Beyonce and Jay-Z generate buzz with virtually everything they do, and their fifth wedding anniversary celebration was no different.

Marking their anniversary in Cuba last week, they caused a stir when they toured Old Havana, posing for pictures with local schoolchildren and dining at the renowned restaurant La Guarida, where police had to step in to keep the crowds at bay, The Associated Press reported.

But the visit has also attracted a more critical audience, two Republican congressman from Florida.

Reps. Ileana Ros-Lehtinen and Mario Diaz-Balart, who represent heavily Cuban districts in South Florida, sent a letter to the federal office responsible for regulating Americans' travel to Cuba asking what kind of license - or special permission - the music power couple had allowing them to travel to the island.

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Unless the U.S. government gives Americans special permission, usually for journalistic, academic, humanitarian or other special reasons that exclude simple tourism, travel to Cuba is prohibited.

Violations of the government's decades-old embargo governing transactions with and travel to Cuba can result in 10 years in prison and $250,000 in individual fines, according to the U.S. Department of the Treasury.

In their letter to Adam J. Szubin, the director of the Office of Foreign Assets Control Department of Treasury - the office that issues licenses for permitted trips to Cuba - Ros-Lehtinen and Diaz-Balart wrote: "We write to express concern and to request information regarding the highly publicized trip by U.S. musicians Beyoncé Knowles-Carter (Beyoncé) and Shawn Carter (Jay-Z) to Cuba. We would like to respectfully request, within all applicable rules and guidelines, information regarding the type of license that Beyoncé and Jay-Z received, for what purpose, and who approved such travel."

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The letter added: "Despite the clear prohibition against tourism in Cuba, numerous press reports described the couple's trip as tourism, and the Castro regime touted it as such in its propaganda. … The restrictions on tourism travel are common-sense measures meant to prevent U.S. dollars from supporting a murderous regime that opposes U.S. security interests at every turn and which ruthlessly suppresses the most basic liberties of speech, assembly, and belief."

Rick Klein, political director for ABC News, said, "I think there is going to be a lot of questions for the administration as to how these two very high-profile, very well-connected individuals got to spend their anniversary in Havana."

A Treasury Department official told ABC News the department does not comment on specific cases.

Beyonce, 31, and Jay-Z, 43, have also not commented on their trip.