Beyoncé and Jay-Z's recent visit to Havana was fully licensed and authorised by the US Treasury department, sources said on Monday. Officials are reportedly preparing a statement on the musicians' Cuban holiday, after complaints by Republican lawmakers.

The stars' controversial trip was legal, a source confirmed to Reuters. Beyoncé and Jay-Z were apparently carrying licences provided by the Treasury's office of foreign assets control, which oversees US citizens' visits to Cuba. The terms of these permits are not clear: Jay Carney, the White House press secretary, called it "a Treasury matter", while the Treasury's spokesman, John Sullivan, told the Associated Press he could not comment on particular licences.

Jay-Z and Beyoncé were reportedly in Cuba to celebrate their fifth wedding anniversary. Although neither star has performed in the country, they were mobbed by fans at La Guarida restaurant in Havana, requiring police back-up. Beyoncé was "beautiful, without a drop of makeup," a waitress told People magazine. According to the Havana Times, the couple also visited the singer Haila Mompié, a children's theatre company, students and teachers at Havana's Superior Art Institute, and the country's national contemporary dance troupe. Reuters' source said they did not have any meetings with Cuban officials.

For more than 50 years, the US has forbidden its citizens from visiting their island neighbour. Under the terms of the US trade embargo, it is not technically illegal for citizens to travel to the communist country, but it is illegal for them to spend money there without special dispensation from the Treasury. Licences are usually restricted to journalists, students, and citizens with Cuban relatives. US tourists commonly circumvent the ban by visiting Cuba via another country, such as Mexico or Canada, and lying to officials upon their return. If discovered, this can result in a prison sentence of up to 10 years.

In an open letter to the office of foreign assets control, two members of Congress called for an investigation into Beyoncé and Jay-Z's Cuban visit. "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," wrote Ileana Ros-Lehtinen and Mario Diaz-Balart. "US dollars spent on Cuban tourism directly fund the machinery of oppression that brutally represses the Cuban people."

On Monday, Florida senator Marco Rubio weighed in on the controversy. The Republican – touted as a possible presidential candidate – tweeted: "If interested in what life really like in Cuba, [Jay-Z] should have visited persecuted rapper Ángel Yunier Remón [Arzuaga] #99problems&dictatorsareone." Remón Arzuaga was allegedly kidnapped by police during a raid last month.

Beyoncé and Jay-Z have declined to comment on their trip.