An exodus from Cuba combined with a virus outbreak put US authorities on full alert Wednesday in a simulation meant to tested the response to a mass migration from the communist-run island.
As part of the Homeland Security exercise off Florida, Coast Guard units took to the seas and military planes flew overhead as fictitious Cubans tried to reach US shores.
The maneuver aimed to test the response to a migration crisis similar to the one in which 125,000 Cubans landed on US shores in the so-called Mariel boatlift in 1980.
Some US officials have speculated there could be a massive migration from Cuba when ailing President Fidel Castro, 80, dies, but officers involved in the exercise declined to discuss that specific scenario.
"I'm not going to get into that," said US Coast Guard (USCG) Rear-Admiral David Kunkel. "This is driven because we have to be prepared," he said at a news conference launching the two-day exercise.
"While this exercise focuses on massive migrations from Cuba ... it could be any Caribbean nation," he said. "However, Cuba is something for which we have to be prepared."
In Wednesday's simulation, 2,000 fictitious Cubans took to the seas in a bid to reach the US Coast, and thousands more people left from Florida to pick up friends and relatives from the Caribbean island.
After about 100 Cubans made it to shore, officials found that a contagious virus had spread among the migrants.
More than 300 officials from some 50 agencies participated in the exercise, which officials said was particularly relevant in south Florida.
In the 1970s, more than 50,000 Haitians fleeing the dictatorship of Francois Duvalier and later his son Jean Claude Duvalier headed to the United States.
In 1980, Castro opened the Cuban port of Mariel, allowing anyone who wanted to leave the country by boat to do so. Over five months, 125,000 people had left the island, some on fragile rafts, others picked up by relatives living in Florida.
A similar migration involving 36,000 Cubans again took place 14 years later, once more placing a huge strain on Miami and other parts of south Florida as authorities tried to cope with the humanitarian crisis.
On August 1, then Florida governor Jeb Bush, a brother of the US president, asked authorities to ready for another such exodus. He made the request one day after Castro announced he had undergone surgery and provisionally handed power to his younger brother Raul.
Kunkel said that at the first sign such a movement could take place, he would seek assistance from the Miami-based military Southern Command.
The aim, he said would be to intercept 95 percent of the migrants and return them to the country they left.
Kunkel insisted there would be no repeat of the Mariel crisis.
"Now we have a plan," he said.
He said that the focus would be to return the migrants to their home countries, but did not rule out using the Guantanamo Bay US military enclave in Cuba to house some of them. In the 1980s and 1990s, the navy base had housed thousands of Cuban and Haitian would-be migrants.
Recent media reports indicated the Pentagon was planning to build facilities on the base to house migrants interdicted at sea.