US intelligence claimed the debilitating "Havana Syndrome," which affected US and Canadian diplomats in several countries around the world, was the result of intense directed energy from an external source. This would support the possibility of deliberate attacks causing the syndrome.

A panel consisting of technological and medical experts convened by the US intelligence community concluded that pulsed electromagnetic energy and ultrasound could cause a unique mix of symptoms in a certain number when delivered from close distances. The symptoms are officially called anomalous health incidents (AHIs), and they range from ear pains to nausea.

Out of hundreds of reported cases, "a subset of AHIs cannot be easily explained by known environmental or medical conditions and could be due to external stimuli," claimed an unclassified summary of the experts' report, released by the US director of national intelligence.

According to the experts behind the study, the creation of concealable devices that would direct electromagnetic energy of ultrasound was possible, and that would cause damage to a targeted person upon using moderate amounts of energy.

The experts, however, did not specify whether such devices exist, nor did they conclude whether such attacks did, in fact, take place or suggest who could have been behind them were they to have taken place.

But the report did reject some statements saying that the AHI attacks taking place are not technologically possible.

The "Havana Syndrome" first surfaced among staff in the US embassy in Cuba in 2016, when US and Canadian diplomats reported suffering from severe headaches, nausea, and possible brain damage after hearing high-pitched sounds.

Many different diplomats and intelligence officials reported similar experiences since then, such as in Australia, Austria, China, Colombia, Germany, and Russia.

The CIA had previously concluded that the "Havana Syndrome" was not caused by a global campaign nor a foreign power, saying it had found plausible explanations in hundreds of cases.

The intelligence agency found that all but about two dozen of some 1,000 reported AHI cases had conventional medical or environmental explanations.

In the report, the experts rejected other theories of causes, including ionizing radiation, chemical and biological agents, infrasound, audible sound, ultrasound propagated over large distances, and bulk heating from electromagnetic energy, saying they were all implausible.