Referring to the assaults, Brown also noted that leadership from the US diplomatic post in Cuba "and supporting offices in Washington believed it was likely a form of harassment by forces hostile to the United States and our presence in Cuba".
Dr. Charles Rosenfarb, medical director of the State Department's bureau of medical affairs, likened the symptoms to those experienced by sufferers of a concussion or mild traumatic brain injury.
Jeff Flake says the US has found no evidence that diplomats in Havana were the victims of attacks with an unknown weapon.
Sen. Jeff Flake, R-Ariz., a supporter of rapprochement with Cuba, has claimed there's no evidence anyone was attacked and that the USA should reverse its decision to withdraw most of its diplomats from Havana.
In a statement provided to CBSMiami, the State Department wrote, "The investigation into the attacks is ongoing".
"At the end of the day, we know that there was an attack, that 24 Americans were hurt when they were working and living in Havana as part of the embassy".
"In late 2016, some members of our diplomatic community serving at U.S. Embassy Havana complained about hearing odd noises and a variety of unexplained physical symptoms". The State Department continues to be deeply concerned about the safety and security of our personnel.
Lawmakers also asked whether rogue elements of the Cuban government or security services or a third party such as Russian Federation might have been involved.
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While Cuban officials have vigorously denied any involvement in the incidents, President Donald Trump said in 2017 that the Cubans were "responsible" for the diplomats falling ill. Marco Rubio concluded must be the product of a rogue element within the Cuban government or another nation-state like Russian Federation operating with Havana's knowledge. Jeff Flake, an Arizona Republican, told CNN on Friday during a trip to the island.
Medical experts and FBI agents launched investigations and high-frequency recording devices were installed in diplomatic residences, allowing a mystery sound sample to be captured.
"Nobody is saying that these people didn't experience some event, but there's no evidence that that was a deliberate attack by somebody, either the Cubans or anybody else", he said. "I will push back on anybody who wants to force me to do that".
A U.S. official told Reuters the government will not send staff back to the U.S. Embassy in Havana yet. The U.S. government has yet to identify an exact mechanism for the attacks.
Rubio and Sen. Bob Menendez, D-N.J., repeatedly pressed Acting Assistant Secretary for Western Hemisphere affairs Francisco Palmieri over the timing and scope of the State Department's response in Havana, and Rubio argued that Secretary of State Rex Tillerson should have set up an Accountability Review Board within 60 days of the US government learning about serious injuries suffered by USA government officials.
Bush and Kasich were focusing on Trump's decision to rescind residency and work protections for about 200,000 Salvadorans invited in by the US after a 2001 quake in a "merciful act".
With so many unanswered questions, the Cuba mystery has become a new front in the decades-old political battle between proponents and opponents of closer ties between the USA and Cuba, two countries estranged for a half-century until relations were restored under President Barack Obama in 2015.
Flake, one of President Donald Trump's toughest Republican critics, announced previous year that he would not seek re-election as Senator from Arizona. He has not ruled out running against Trump in 2020.
Starting in 2016, those two dozen United States diplomats and their spouses in Havana reported the injuries, with news accounts blaming "sonic attacks" and reporting concussion-like symptoms, such as nausea, vertigo, and loss of hearing in one ear, among diplomats. But officials are now carefully avoiding that term.