(CNN) — Cuban forces shot dead four people in a Florida-registered speedboat that entered Cuban waters Wednesday in a dramatic shoot out just off the island’s coast. The nationalities of those killed is not yet known, but U.S. Secretary of State Marco Rubio said the U.S. embassy in Havan a is working to get access to other people who were aboard the vessel to determine whether they are American citizens or permanent residents. “As we gather more information we will be prepared to respond to accordingly,” Rubio said. “We’re going to figure out exactly what happened.” The incident comes amid heightened tensions between the U.S. and Cuba as Washington has blocked virtually all oil shipments from reaching the communist-run island. The oil shortage has brought Cuba’s economy to its knees, with the Caribbean nation experiencing its worst era of economic uncertainty in decades. Six other people aboard the vessel were injured and are receiving medical attention. Cuban border guard troops approached the boat to identify it after it entered Cuban territorial waters in Falcones Cay, Villa Clara Province, the ministry said. Falcones Cay is just over 100 miles from Florida. The Cuban forces were then shot at by someone from the boat, injuring the commander of the Cuban boat, the statement said. The border guards then returned fire. Rubio said the U.S. “immediately” began looking into the incident after being informed of it by Cuban authorities. The U.S. Department of Homeland Security and the U.S. Coast Guard are also involved. Rubio is currently in the region, on an official visit to Saint Kitts and Nevis. U.S. Vice President JD Vance said the White House was “monitoring” the situation but details are still scarce. “(It is) certainly, you know, a situation that we’re monitoring, hopefully it’s not as bad we fear it could be. But (I) can’t say more, because I just don’t know more,” Vance said during an unrelated event at the White House. The boat, with registration number FL7726SH, is a 24-foot power boat that was manufactured in 1981, according maritime database records. “In light of the current challenges, Cuba reaffirms its willingness to protect its territorial waters, based on the fact that national defense is a fundamental pillar for the Cuban state in favor of protecting its sovereignty and stability in the region,” the Cuban interior ministry said. Florida officials express alarm Officials from Florida called for an investigation and for the Cuban government to be held accountable. Florida Attorney General James Uthmeier said he has directed the Office of Statewide Prosecution to help federal, state, and law enforcmeent authorities begin an investigation. U.S. Republican Rep. Carlos A. Gimenez, whose district includes the southern tip of Florida, said the incident raised concerns about the use of lethal force against people aboard a U.S.-registered vessel and called for an investigation into the incident. “United States authorities must determine whether any of the victims were U.S. citizens or legal residents and establish exactly what occurred,” he said in a statement posted to X. “The regime in Cuba must be relegated to the dustbin of history for its countless crimes against humanity.” U.S. Republican Sen. Rick Scott, also from Florida, called the incident “deeply concerning” and said the Cuban government “must be held accountable.” Cuba’s interior ministry said authorities are investigating the incident. ...read more read less