The CIA has released a report on a mystery virus that has allegedly struck down 1,000 US diplomats.
The so-called "Havana Syndrome" has been reported to cause headaches, dizziness, nausea and other symptoms consistent with traumatic brain injuries.
It first came to public attention in 2016 after dozens of diplomats became unwell while working at the US Embassy in Havana, Cuba.
However, despite allegations swirling about malicious Russian or Chinese involvement in the spread of the virus, the CIA has concluded that the Kremlin is not to blame, the Express reports.
Intelligence officials instead say that most cases of the illness can be explained by environmental causes, undiagnosed medical conditions or stress, rather than actions by a foreign power.
However, CIA Director William Burns said that the agency's findings were "interim" and that their investigation would continue.
“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."
The report's conclusions have angered some of those who have fallen ill.
A group representing those struck down with the sickness, Advocacy for Victims of Havana Syndrome, said that the CIA report "must not be the final word on the matter".
“The CIA’s newly issued report may be labeled ‘interim’ and it may leave open the door for some alternative explanation in some cases," the group said. "But to scores of dedicated public servants, their families and their colleagues, it has a ring of finality and repudiation."
Some believe the syndrome is purely psychosomatic - a physical reaction to a psychological ailment such as anxiety or stress.
However, Bill Evanina, a former senior US intelligence official, said he believes there is a more sinister explanation for the phenomenon.
“Was it an offensive weapon in some manner or form targeted to individuals? I believe it was," he said.
“You may ask yourself if the Russian government was increasing and propagating their intelligence operation in Cuba, probably not good for them to have the US in Cuba in mass to identify some of the things that have happened there."
Russia and China have both denied any involvement.
For stories from where you live, visit InYourArea.
