HAVANA -- A group of men captured in February after attempting to enter Cuba by force from the United States have confessed and cooperated with investigators, Cuban authorities said Monday, adding that forensic examinations found the seized weapons and explosives were powerful and operational.

The men could face terrorism-related charges involving deadly devices and explosives under Cuba’s penal code, Col. Francisco Estrada Portales, an official with the Interior Ministry’s State Security department, told The Associated Press.

The offenses can carry the death penalty, but Estrada said prosecutors had not yet requested specific sentences. Cuba has not carried out an execution in decades.

A speedboat carrying 10 men of Cuban origin from the United States attempted to enter Cuban waters on Feb. 25 and opened fire on a Cuban coast guard vessel that tried to intercept it, authorities said. Three of the attackers were killed in the confrontation, and a fourth later died of his injuries. The boat was about 1.6 kilometers (1 mile) northeast of Cayo Falcones, off Cuba’s northern coast.

The captain of the Cuban coast guard vessel was wounded. Authorities also reported arresting a person on land who allegedly provided support to the group.

The incident came as tensions between Cuba and the United States intensified, with Washington imposing energy restrictions on the island as part of its campaign to force a change in government and not ruling out military action.

Cuba’s Interior Ministry previously displayed weapons and equipment seized from the group, including rifles, handguns, explosives, backpacks containing clothing, uniforms, boots, helmets, medical supplies, food, an electric generator, satellite communications equipment and thousands of rounds of ammunition.

“The weapons and explosives were all in good working condition and ready to be used to cause harm,” Estrada said.

Estrada said the suspects’ confessions and cooperation helped investigators determine that Amijail Sánchez, a Cuban who has lived in the United States since 2016, fired the first shots. Sánchez, who is in custody, was included on a list of alleged terrorists that Cuba submitted to the United Nations last year.

Another detained suspect, Leordan Cruz, also appears on Cuba’s terrorism list.

Cuban authorities showed AP video recordings of statements made by the suspects. AP could not independently verify the contents of the recordings or the circumstances under which the statements were made.

In one recording, Cruz said the group intended to secure an area and encourage Cubans to overthrow the government.

Estrada said Cuban authorities had shared their findings with the United States but had received no response as of Monday.

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