The CIA has determined it’s unlikely that “Havana Syndrome,” a mysterious set of symptoms first detected among U.S. diplomats in Cuba, is the result of a sustained global campaign by a hostile foreign actor, NBC News and The New York Times reported late Wednesday, citing CIA officials familiar with a new intelligence assessment. 

Most of the 1,000 cases reported by U.S. diplomats and spies have plausible, alternate explanations, like undiagnosed medical conditions, environmental causes, or stress. But “in about two dozen cases, the agency can’t rule out foreign involvement, including many of the cases that originated at the U.S. embassy in Havana beginning in 2016,” NBC News reports.

“We assess it is unlikely that a foreign actor, including Russia, is conducting a sustained, worldwide campaign harming U.S. personnel with a weapon or mechanism,” a senior CIA official tells The Washington Post. The CIA is focusing now on the two dozen unexplained cases that “offer the greatest chance of yielding clues to whether a foreign power is responsible” for the mysterious maladies, the Times reports.

The CIA’s interim reports is “not a final conclusion of the broader Biden administration or the full intelligence community,” NBC News reports, and an expert panel convened by the White House National Security Council is still examining Havana Syndrome, as are the Pentagon, FBI, and State Department. Still, the Times says, the CIA’s assessment “left many victims dissatisfied, particularly current and former officials who have been battling chronic ailments for years without being given a clear explanation.”

CIA Directors William Burns, who has publicly characterized Havana Syndrome as an attack, said in a statement that “
“while we have reached some significant interim findings, we are not done.” He noted that CIA officers have experience real symptoms, adding, “We will continue the mission to investigate these incidents and provide access to world-class care for those who need it.”

Marc Polymeropoulos, a former CIA officer afflicted with Havana Syndrome symptoms on a 2017 trip to Moscow, told the Times “it took us 10 years to find Osama bin Laden,” so “I would just urge patience and continued investigation by the intelligence community and the Department of Defense.”