Feb. 2 (UPI) -- An external energy source plausibly could be the cause for a series of disorienting and sometimes debilitating symptoms experienced by U.S. government personnel, a panel of experts announced Wednesday.
In a report released Wednesday, the expert panel, convened by U.S. intelligence agencies said the symptoms described in these Anomalous Health Incidents, also known as "Havana Syndrome," are common in known medical conditions.
But the combination of "four core characteristics" is unique and make it unlikely to be caused by a neurological disorder, the report said.
The panel, composed of experts from within and outside the U.S. government with backgrounds in in science, medicine and engineering, was tasked with examining the cases dating to 2016 that have affected personnel at the U.S. Embassy in Cuba, followed by reports from personnel in China and eventually hundreds of people at official posts throughout the world.
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In its examination, the panel examined four "core characteristics" of symptoms that "were particularly difficult to explain through other means" such as sound or pressure in the ears, "nearly simultaneous" symptoms including vertigo, loss of balance and ear pain, "a strong sense of locality or directionality" among those symptoms, and absence of known environmental or medical conditions that may have caused the symptoms.
Additionally, the panel examined the plausibility of five "potential causal mechanisms" for the symptoms, including acoustic signals, chemical and biological agents, ionizing radiation, natural and environmental factors and radio frequency and other electromagnetic energy.
Pulsed electromagnetic energy "plausibly explains the core characteristics," according to the panel's findings, as there are several possible pathways that "could generate the required stimulus, are concealable and have moderate power requirements."
The panel also said signals could be propagated with low loss through the air for tens to hundreds of meters, and with some loss through building materials via the use of "nonstandard" antennas and techniques.
Ultrasound was another potential cause, but would likely only be effective in close range and would not explain reports of personnel experiencing symptoms while inside buildings, the report said.
Potential causes such as psychological factors on their own, ionizing radiation, chemical and biological agents, infrasound and audible sound also were deemed implausible.
The panel did not examine or produce any speculation about whether the symptoms were caused by a foreign nation.
In January, a report by the Central Intelligence Agency stated that many of the cases were likely not caused by a foreign adversary and instead could probably be attributed to environmental causes, undiagnosed medical conditions or stress.
Avril Haines, director of national intelligence and William J. Burns, director of the CIA said in a joint statement that investigation into the symptoms will continue.
"The U.S. government remains committed to providing access to care for those who need it, and we will continue to share as much information as possible with our workforce and the American public as our efforts continue. Nothing is more important than the well-being and safety of our colleagues," they wrote.