The State Department says it expelled two Cuban diplomats earlier this year for unspecified incidents starting in 2016.
A spokesperson for the State Department's Bureau of Western Hemisphere Affairs says the department does not have "definitive answers on the source or cause of the incidents".
"We have reminded the Cuban government on various occasions that, under the Vienna Convention, this type of treatment of diplomatic personnel is unacceptable", the State Department official said at the time.
After months of investigation, United States officials concluded that the diplomats had been attacked with an advanced sonic weapon that operated outside the range of audible sound and had been deployed either inside or outside their residences.
The official said the State Department's office of Diplomatic Security has the lead on the investigation.
USA officials believe a group of American diplomats in Havana suffered severe hearing loss after being exposed to a covert sonic device.
The United States and Cuba officially resumed a diplomatic relationship in July 2015, more than five decades after they severed it, during the administration of then U.S. President Barack Obama. "We asked two officials who were accredited at the Embassy of Cuba in the United States to depart the United States".
The Cuban government has so far refused to comment on the reports, or the expulsion of its diplomats.
The Cuban authorities set up an inter-institutional expert committee for the analysis of the facts; expanded and reinforced the protection and security measures of the mission, its staff and diplomatic residences; and new channels were made available for direct communication between the Embassy and the Department of Diplomatic Security.
"We have some Americans who choose to come home as a result of that", said Nauert. Those officials have left the country. She added a reminder that "the Cuban government has a responsibility and obligation to protect our diplomats". "We take those incidents very seriously and there is an investigation now underway". The US has kicked out two Cuban diplomats in an attempt to address the odd incidents.
Cuba said it had started a comprehensive investigation into the alleged incidents after it had been informed of them by the embassy in February.