Doctors and scientists say that microwave weapons are the main suspect behind the mysterious ailments of dozens of American diplomats and family members in Cuba and China.

Douglas Smith, director of the Center for Brain Injury and Repair at the University of Pennsylvania, told The New York Times that microwaves were likely behind the health incidents, some of which likely resulted in brain injury.

Smith was the lead author of a study that examined 21 affected U.S. diplomats from Cuba. The study, published in The Journal of the American Medical Association in March, did not mention microwaves.

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“Everybody was relatively skeptical at first, and everyone now agrees there’s something there,” Smith told the Times.

Experts told the Times that microwave strikes likely explain why some Americans in Cuba and China reported hearing painful sounds, loss of hearing, vertigo and other ailments. Investigators previously speculated that the attacks were caused by sonic waves or viral infections.

The Times reported that some analysts cited the "Frey effect" as a possible explanation behind the reported illnesses. The phenomenon is named for American scientist Allan Frey, who discovered that microwaves can cause the brain to perceive what appear to be ordinary sounds, such as loud noises like ringing or buzzing, the paper noted.

It is still unclear who is responsible for the attacks.

"The health and well-being of our personnel remains our top priority," a State Department official said in a statement to The Hill. "The investigation into the origin of these symptoms continues. The inter-agency community is working diligently to determine the cause of the symptoms, as well as to develop mitigation strategies.”

The attacks at the U.S. embassy in Havana resulted in a diplomatic row in which Washington late last year. At the time, the Trump administration announced it would drastically reduce its diplomatic staff in Cuba and expel more than a dozen Cuban diplomats over months of alleged "health attacks" directed at U.S. personnel.

The Cuban government, which is conducting an individual investigation into the matter, has denied any role in the incidents and has accused the U.S. of playing politics with the cases.