Tourists drive in classic convertible cars on the Malecon beside the U.S. Embassy in Havana, Cuba, this month. Desmond Boylan AP
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The State Department said the “safety and well being of American citizens” is the department’s top priority.

“We are continuing our investigation into the attacks and the Executive branch has and will continue to brief Congress about these attacks,” said a spokesperson for the State Department’s Bureau of Western Hemisphere Affairs.

A series of mysterious “sonic” attacks began months ago and has affected as many as 25 U.S. personnel. According to one source, U.S. intelligence operatives were the first known Americans affected. The most recent incidents were reported within the last few weeks.

The United States still does not know the nature of the device or weapon being employed against its staff.

The Associated Press has obtained a recording of what some U.S. embassy workers heard in Havana as they were attacked by what investigators initially believed was a sonic weapon.

Earlier this month, the Trump administration kicked nearly two-thirds of Cuba’s embassy personnel out of the United States after pulling many American diplomats from the U.S. embassy in Havana.

The State Department has not accused Cuba of being behind the incidents. But it has repeatedly warned that Havana is responsible for the safety of foreign diplomats on its soil under the Vienna convention on diplomatic relations.

Ros-Lehtinen and Sires said they want the GAO to investigate the timeline of events, how State responded when the attacks began, and what steps State took to address the medical needs of U.S. personnel and citizens.

“It is not new that the Castro regime undermines our national security at every turn and has always posed a threat to U.S. citizens in Cuba so it is no surprise that Havana cannot protect and ensure the safety of U.S. personnel under its Vienna obligations,” Ros-Lehtinen and Sires said. “We must ensure that the necessary policies are in place to ensure the safety of our government personnel and all U.S. citizens overseas.”