(CN) – U.S and Canadian diplomats in Cuba suffered mild traumatic brain and central nervous system injuries in a fall 2016 incident investigated as a sonic attack, published reports say.
The State Department said at least 10 U.S. diplomats and five from Canada who were posted in Havana began experiencing “a variety of physical symptoms” including nausea, hearing loss, headaches, and problems with their equilibrium.
A months-long investigation led the U.S. to conclude they were “exposed to an advanced device that operated outside the range of audible sound.”
The Cuban government has said it was not responsible for any possible attack on the diplomats, but Secretary of State Rex Tillerson is pressing the government to get to bottom of what he described as “health attacks.”
In response Cuban officials said they have begun an “exhaustive, high-priority, urgent investigation” into the the apparent use of a sonic device aimed at diplomatic residences in Havana.
Although the State Department has not officially blamed the Cuban government, the U.S. expelled two Cuban diplomats in May in connection to the attacks, reported the Washington Post.
In addition, some diplomatic tours of duty have also been cut short as a result of the incident.
According to New Scientist magazine there are two ways that hearing loss could be effected without people knowing it: The first is with sound waves at a frequency too low for humans to hear; the other is to use ultrasound frequencies above the range of human hearing.