Whatever the cause of the puzzling symptoms dubbed the “Havana syndrome,” the U.S. intelligence community has concluded it was not a secret weapon used by a foreign adversary, the Washington Post reported Wednesday, citing officials known to were with the report.

The final report on the matter “destroys a long-disputed theory” that some kind of Russian energy weapon was to blame, according to the Post. However, some State Department officials continue to believe that “a foreign government, probably Russia,” is to blame, pointing out that the number of reported cases has fallen after the conflict in Ukraine escalated last February.

According to the outlet, a total of seven intelligence agencies participated in the investigation. A special group of seasoned analysts, led by a senior CIA officer, “dedicated extraordinary resources” to find the possible cause, by looking at about 1,000 cases of what Washington has mentioned “abnormal health incidents” (AHI). They eventually found it “no pattern to link reported cases to a possible cause”, said the Post.

Five of the authorities involved said yes “very unlikely” a foreign actor was responsible. An agency said it was common “unlikely,” while one bureau abstained. However, none of them disagreed with that conclusion “a foreign actor did not cause the symptoms”, an official told the paper.

For years, hundreds of U.S. diplomats, intelligence officers, and other personnel at embassies on every continent have reported headaches, nausea, ringing in the ears, and even brain damage caused by strange noises. The term “Havana Syndrome” was coined because the first reports came from the recently reopened US Embassy in Cuba in 2016. Some of those affected claimed they were the target of a deliberate attack, by Russia or another adversary, using sonic weapons. The final report contradicts that claim “in almost every way”, the Post sources said.

Intelligence analysts found “no pattern or common set of conditions that might tie individual cases together” And “no evidence, including forensic information or geolocation data”, that would suggest the use of directed energy, including radio waves and ultrasonic beams. There was no evidence even in places where the US had it “total ability to monitor the environment” for malicious activity.

“There was nothing,” one of the officials told the Post.

In addition, none of the authorities considered it likely that Russia or China had an energy weapon that could cause the symptoms. Medical experts could not attribute the described symptoms to an external factor “unrelated to any pre-existing condition or environmental factors,” the found report.

The directed energy hypothesis was bolstered by a 2020 report from a panel of the National Academies of Sciences, Engineering and Medicine, which found a “targeted, pulsed radio frequency (RF) energy” was blamed. However, other experts quickly cast doubt on that theory.

In September 2021, BuzzFeed published a declassified report by JASON, a State Department advisory group, which concluded that the “highly unlikely” the reported symptoms were caused by microwaves or ultrasonic rays. The report, prepared in November 2018, was eventually classified and not shared with the NASEM panel.

According to JASON’s report, local crickets were the most likely culprit in a third of reported cases in Havana. This was consistent with the 2017 conclusion of experts in California, who identified the sound released by the Associated Press as the mating call of the male Indian short-tailed cricket.

In the meantime, Congress created a fund to compensate those who reported “Havana Syndrome” symptoms, and a compensation package of more than $100,000 was reportedly announced last summer.