The US Embassy in Cuba (archive photo): This is where the first reports of mysterious symptoms of illness among American diplomats were made in 2016
Photo: Desmond Boylan / dpa
According to media reports, the US foreign intelligence service CIA does not currently assume that a foreign country is responsible for the so-called Havana syndrome.
The CIA has no corresponding evidence, it said in US media, citing an interim report.
Most of the mysterious illnesses of embassy staff appear to be due to previously undiagnosed illnesses or stress.
However, there are also cases that cannot be explained, according to the interim report.
However, it is unlikely that this will be a sustained global campaign.
Dozens of US diplomats and their families living in Havana have complained of mysterious headaches, hearing loss, dizziness and nausea as of 2016.
The embassy staff there was then reduced to a minimum.
Similar complaints were later reported by US diplomats elsewhere in the world, with cases reported from China, Germany, Australia, Russia, Colombia, Austria and Washington.
The government in Washington did not rule out that this could be some kind of attack - but it always emphasized that they did not know what was behind it.
A senior US foreign intelligence official told AFP on Thursday: "We have determined that it is unlikely that any foreign actor, including Russia, is conducting a sustained global campaign in which US personnel are armed or... a mechanism is damaged.« Politicians and victim representatives in Washington reacted sceptically, however.
Attorneys for alleged victims dismissed the CIA's conclusions.
The CIA released it to deal with a "revolt among its staff because the officers don't want to go overseas," said attorney Mark Zaid.
"The CIA report is disinformation," he said, noting that others in the US intelligence community disagree with the report.
Members of the Senate and House Intelligence Committees briefed on the findings of the CIA report on Wednesday expressed some reservations about the report.
Republican Senator Susan Collins said she was "surprised" by the conclusions.
"It is difficult to reconcile the findings of the CIA's expert task force with other evidence and statements," she said.
According to Foreign Minister Blinken, investigations will continue
When asked on Thursday, US Secretary of State Antony Blinken did not go directly into the results of the report.
However, he announced that the investigation would continue.
"When you talk to people, when you hear what they've been through, there's no doubt in my mind that they've had real experiences, real symptoms and real suffering," he said.
"We will continue to do everything we can to understand what happened, why it happened and who might be responsible."