When their symptoms became severe in the fall of 2016, leading some to return home, USA officials began an investigation as to why.
The U.S. Embassy in Havana was reopened in 2015 following then-President Barack Obama's normalizing of relations with Cuba. But diplomats said that after the usa and Cuba restored full diplomatic ties in 2015, the campaign of harassment stopped. On Wednesday, Nauert said the physical symptoms are non-life threatening. "The AP says Cuba may have placed sonic devices that produce non-audible sound inside or outside the residences of several embassy staffers with the intent of deafening them", he reported.
It was not immediately clear if the device was a weapon used in a deliberate attack, or had some other objective.
Some subsequently got hearing aids, said the official, who spoke on condition of anonymity.
Officials are also looking into the possibility that the incidents were carried out by a third country such as Russian Federation, possible without the knowledge of Cuban officials.
U.S. officials told The Associated Press that about five diplomats, several with spouses, had been affected and that no children had been involved. In her cagey comments yesterday, Nauert would only refer to an "incident" in which diplomats experienced "physical symptoms".
The investigation into the matter is ongoing and the United States has no definitive answers to the cause of the physical symptoms experienced by USA government workers, Nauert added.
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Nauert said the affected staff received medical examinations and are being monitored as officials continue to investigate the cause.
No children were affected, but at least some of the adults who were are believed to have suffered permanent hearing loss, according to the officials.
"We requested their [Cuban diplomats'] departure as a reciprocal measure since some U.S. personnel's assignments in Havana had to be curtailed due to these incidents", said Nauert.
Cuba denies the allegation, but the U.S. has removed two Cuban diplomats from Washington DC in retaliation. But she could not elaborate on the nature or cause of the incidents.
"We don't have any definitive information about the source or the cause", she said. When asked specifically what the incidents were, Nauert replied, "That's what we're calling it".
The US has also since expelled two Washington-based Cuban diplomats.
Global Affairs Canada, the coutnry's foreign ministry, says the government is working with the USA and Cuban governments to find out what happened. Buzzfeed News reported on Wednesday that the global community has gotten the impression Trump is really only focused on undoing anything that was started by the Obama administration.
State department employees in Havana began complaining of hearing loss, constant painful headaches, and other issues late previous year.