A top U.S. diplomatic security official said on Tuesday that investigators looking into a string of mysterious illnesses experienced by American diplomats in Havana are probing a number of possibilities for what might have caused the ailments.
Todd Brown, the State Department’s assistant director of diplomatic security, told a Senate panel that the possibility of “viral” or “ultrasound” attacks are among the causes being looked at.
Some U.S. officials and investigators initially suspected that some of the illnesses may have been caused by a covert, sonic attack, because several of the affected individuals reported hearing a loud noise before experiencing symptoms.
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A recent FBI report revealed, however, that investigators have not found evidence to support that theory, according to The Associated Press. Brown said that a number of other types of attacks are being investigated.
“I think there’s viral, there’s ultrasound,” he told members of a Senate Foreign Relations subcommittee. “There’s a range of things that technical experts are looking at as, ‘could this be a possibility?’ “
American diplomats in Havana began experiencing symptoms in the fall of 2016, with the most recently reported case happening in August. So far, 24 cases have been confirmed by the State Department.
The mysterious illnesses have driven a wedge in the newly re-established relations between the U.S. and Cuba. Secretary of State Rex Tillerson has said that the Cubans could have prevented the incidents, while the Cuban government has argued that it had no knowledge of, or involvement in, the incidents.
The U.S. moved in September to withdraw most of its diplomatic staff from the embassy in Havana, and soon after expelled a number of Cuban diplomats from Washington.