The CIA has found that it is unlikely that Russia or another "foreign actor" caused most of the anomalous health incidents that have afflicted US diplomats and intelligence officers worldwide for years, an official with the spy agency said on Thursday.
The official, describing the conclusions of an interim report on so-called Havana Syndrome, said a majority of 1,000 cases "can be reasonably explained by medical conditions or environmental and technical factors, including previously undiagnosed illnesses."
"We have so far not found evidence of state actor involvement in any incidents," the official continued. "The finding does not call into question the fact that our officers are reporting real experiences and are suffering real symptoms."
The CIA is continuing to investigate two dozen unexplained cases that could offer further clues into whether any foreign countries are involved, added the official, who spoke on condition of anonymity.
"We have not ruled out the involvement of a foreign actor in these cases," the official said.
Speaking at a news conference in Berlin, Secretary of State Antony Blinken vowed that the US government would continue to investigate the matter.
"We will leave no stone unturned to get to the bottom of it," said Blinken, who was in Berlin as part of a series of meetings regarding Russia and Ukraine.
The mysterious ailment, first reported among US officials in the Cuban capital in 2016, has afflicted US diplomats, officials and family members overseas. Symptoms have included migraines, nausea, memory lapses and dizziness.
"We are going to continue to do everything we can with all the resources we can bring to bear to understand, again, what happened, why and who might be responsible," Blinken said, adding that the State Department would continue to focus on making sure those afflicted get needed healthcare.
CIA Director William Burns made a similar pledge.
"While we have reached some significant interim findings, we are not done," Burns said in a statement. "We will continue the mission to investigate these incidents and provide access to world-class care for those who need it."