The US government is investigating whether American diplomats serving in Cuba were victims of an attack that damaged their hearing and caused other physical symptoms, officials said Thursday.
The two-year thaw in diplomatic ties was strained after The Associated Press reported that officials had concluded that the Americans in Havana were targeted by a ''covert sonic weapon''. AP described the suspected weapon or device as something that could not be heard by the victims.
In the fall of 2016, a series of US diplomats began suffering unexplained losses of hearing, the report said, citing officials with knowledge of the investigation into the case. Several of the diplomats were recent arrivals at the embassy, which reopened in 2015 as part of former President Barack Obama's reestablishment of diplomatic relations with Cuba.
Some of the diplomats' symptoms were so severe that they were forced to cancel their tours early and return to the United States, officials said. After months of investigation, US officials concluded that the diplomats had been exposed to an advanced device that operated outside the range of audible sound and had been deployed either inside or outside their residences. It was not immediately clear if the device was a weapon used in a deliberate attack, or had some other purpose.
A US official confirmed to The Washington Post that the diplomats suffered hearing damage and neurological symptoms that remain unexplained.
The official did not identify a covert weapon as the suspected cause but said ongoing FBI and State Department investigations are looking at the incidents as an attack. The official spoke on the condition of anonymity because of a lack of authorization to discuss the investigations on the record.
State Department spokeswoman Heather Nauert said the US retaliated by expelling two Cuban diplomats from their embassy in Washington on 23 May. She did not say how many US diplomats were affected or confirm they had suffered hearing loss, saying only that they had ''a variety of physical symptoms''.
The Cuban government said in a lengthy statement late Wednesday that ''Cuba has never permitted, nor will permit, that Cuban territory be used for any action against accredited diplomatic officials or their families, with no exception.''
The statement from the Cuban foreign ministry said it had been informed of the incidents on 17 February and had launched an ''exhaustive, high-priority, urgent investigation at the behest of the highest level of the Cuban government.''
It said the decision to expel two Cuban diplomats was ''unjustified and baseless''.
The ministry said it had created an expert committee to analyse the incidents and had reinforced security around the US embassy and US diplomatic residences.
''Cuba is universally considered a safe destination for visitors and foreign diplomats, including US citizens,'' the statement said.
US officials told AP that about five diplomats, several with spouses, had been affected and that no children had been involved. The FBI and Diplomatic Security Service are investigating.
Cuba employs a state security apparatus that keeps many people under surveillance and US diplomats are among the most closely monitored people on the island, according to AP. Like virtually all foreign diplomats in Cuba, the victims of the incidents lived in housing owned and maintained by the Cuban government.
When it comes to sound, the human body can be very fragile outside a narrow range. Certain low frequencies can lead to balance problems, soft-tissue pain and disturbed visual function. High ones can produce a powerful shock wave that can physically damage the ear.
However, Seth Horowitz, a former professor of neuroscience at Brown University, told The Washington Post that ''there are no acoustic devices that can cause sudden onset hearing loss that the people involved could not hear'', and he expressed scepticism about the State Department's claims.
Horowitz explained that infrasonic machines at a very high amplitude can cause nausea, ultrasonics have no effect on hearing, and long-range acoustic devices or sound canons are ''extremely noticeable and easy to move away from''.
''It's tragic,'' he said of the reports, ''but it can happen from viruses, genetic predisposition, an accident, exposure to urban noise.''