Two Cuban diplomats were kicked out of the Washington embassy by the State Department after a series of incidents forced U.S. officials in Cuba to return home with “a variety of physical symptoms,” State Department officials said Wednesday.

Starting in the fall of 2016, American diplomats in Havana suffered from severe hearing loss attributed to a covert sonic device, the Associated Press reported.

Following months of investigation, U.S. 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.

The Cuban diplomats, meantime, were ordered to leave the U.S. on May 23, the officials said.

State Department spokeswoman Heather Nauert said more incidents followed the initial ones in 2016, prompting the Americans to leave the island and the department to act against the Cuban diplomats in the U.S.

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Nauert confirmed the report Wednesday during a briefing. She did not go into details but did say Cuba has been reminded of its obligation under the Geneva Convention to protect foreign diplomats. She said the department is looking into the matter.

“One of the things we talk about here often is that the safety and security of American citizens, at home and abroad, is our top priority," she said. "We’re taking that situation seriously, and it’s under investigation right now.”

Fox News can confirm that the FBI is now investigating.

The Cuban government has assured the U.S. that it is looking into the reports and will take appropriate measures, officials said.

Cuba's Ministry of Foreign Affairs released a statement on Wednesday night, detailing the series of events that they claimed led to their diplomats being removed.

The May decision to have the diplomats removed, Cuba claimed, was "unjustified and unsubstantiated."

"Cuba has never, nor would it ever, allow that the Cuban territory be used for any action against accredited diplomatic agents or their families, without exception," the Ministry said. "Moreover, it reiterates its willingness to cooperate in the clarification of this situation."

Fox News' Nicholas Kalman and The Associated Press contributed to this report.