Cuba’s government said a Florida-registered speedboat that entered Cuban waters opened fire on Cuban soldiers, killing four people and wounding six, and it later described the boat’s occupants as armed Cubans living in the United States who were attempting to infiltrate the island. Cuba said late Wednesday that the 10 passengers were trying to “unleash terrorism,” and it said the majority had a “known history of criminal and violent activity.”

The announcement came hours after Cuba said its soldiers killed four people and wounded six others aboard the speedboat, which it said entered Cuban waters and shot first, injuring one Cuban officer. Cuba identified one of the four killed as Michel Ortega Casanova and said the investigation “continues until the facts are fully clarified,” according to a ministry statement.

U.S. Secretary of State Marco Rubio said the United States is working to verify details independently, including whether the victims were American citizens or permanent residents. Rubio told reporters earlier that “we have various different elements of the U.S. government that are trying to identify elements of the story that may not be provided to us now,” adding that the U.S. was gathering its own information.

Rubio said the U.S. would not rely solely on Cuba’s account. “The majority of the facts being publicly reported are those by the information provided by the Cubans. We will verify that independently as we gather more information, and we’ll be prepared to respond accordingly,” he said, adding that “we’re going to have our own information on this” and determine “exactly what happened.”

Cuba named multiple passengers and described alleged links to terrorism. It identified two passengers as Amijail Sánchez González and Leordan Enrique Cruz Gómez, saying they were wanted by Cuban authorities “based on their involvement in the promotion, planning, organization, financing, support or commission of actions” connected to terrorism. Cuba also said it arrested Duniel Hernández Santos and that he “was sent from the United States” to ensure the reception of the “armed infiltration,” adding that he “has confessed to his actions,” though The Associated Press said it could not independently verify Cuba’s claims.

In addition, Cuba said it identified seven of the 10 passengers, including Conrado Galindo Sariol, José Manuel Rodríguez Castelló, Cristian Ernesto Acosta Guevara and Roberto Álvarez Ávila. On Thursday, Cuba’s deputy foreign minister, Carlos Fernández de Cossío, said Cuba had made an error in its earlier identification, saying it “erroneously identified Roberto Azcorra Consuegra as one of the boat passengers late Wednesday,” and that Azcorra was not aboard the boat.

Rubio described the incident as highly unusual. He said it was “highly unusual to see shootouts in open sea like that,” noting that it was “not something that happens every day” and that it “hasn’t happened with Cuba in a very long time.” He said the U.S. Department of Homeland Security and the U.S. Coast Guard are investigating and that he wanted to verify the facts.

Cuba also said earlier that the boat was roughly 1.6 kilometers (1 mile) northeast of Cayo Falcones off Cuba’s north coast, and it provided a registration number, though The Associated Press said it was unable to readily verify the vessel details because Florida boat registrations are not public. Cuba’s Interior Ministry said its government was “safeguarding its sovereignty and ensuring stability in the region,” and the U.S. Attorney’s Office for the Southern District of Florida said it would pursue answers “through every legal and diplomatic channel available,” while adding that “facts remain unclear and conflicting.”

The shooting threatens to raise tensions between the U.S. and Cuba as the Trump administration has taken a more aggressive approach toward Havana. The Associated Press reported that the energy crisis Cuba has faced in recent years entered new extremes after Trump signed an executive order last month imposing a tariff on any country that sells or provides oil to Cuba, and it said Cuba had become heavily dependent on petroleum shipments from Mexico after Trump halted oil shipments from Venezuela.