MIAMI — A group of doctors and scientists who first evaluated U.S. embassy workers evacuated from Cuba say their symptoms and medical findings "cannot be faked," and that whatever happened to them resulted in measurable injury to their inner ears.

Two years after U.S. diplomats and spies in Havana started experiencing strange sounds and sensations and then falling ill, doctors at the University of Miami said Wednesday they still don't know what happened to them or what caused their injuries. But they say that "objective signs" rule out the possibility of mass hysteria and prove that something affected the patients' vestibular, cognitive and emotional functioning.

"These tests that we did cannot be faked," Dr. Michael Hoffer, an ear, nose and throat specialist at the University of Miami, said in a news conference coinciding with the release of a new study by Hoffer and his colleagues in the medical journal Laryngoscope Investigative Otolaryngology. "We have measurable, quantifiable evidence that something really did happen."

But the doctors and scientists acknowledged they can't say for sure what kind of weapon caused the damage — or whether it was a weapon at all. The U.S. government calls the incidents in Cuba "targeted health attacks," and NBC News has reported that the U.S. believes sophisticated microwaves or another type of electromagnetic weapon may have been used.

The State Department says it doesn't know who is to blame. Cuba adamantly denies any knowledge or involvement in any attacks. In a news conference in Havana on Wednesday, the top Cuban diplomat for U.S. affairs, Carlos Fernandez de Cossio, said the U.S. approach to the issue has been full of "speculation or manipulated information."

"I'm agnostic about what may have happened," said Carey Balaban, a Ph.D. scientist who teaches neurobiology at the University of Pittsburgh and developed the article with Hoffer. "I'll tell you right off the — I don't know."

Balaban said his team's conclusion is that some form of "directed energy" focused on an object or a person caused the damage.

"The energy may be acoustic. Pressure waves," Balaban said. "You've probably heard of LRAD devices. We also could have radio frequency. We could have microwave. We could have light."

Hoffer, a former military doctor who studied traumatic brain injury in Iraq War blast victims, was the doctor first enlisted by the State Department in early 2017 to try to figure out what had happened to U.S. embassy workers in Havana after they started reporting sounds and symptoms. He traveled to Cuba to examine patients, and many came to Miami for full evaluation at the university.

Ultimately, the State Department stopped sending patients to Hoffer and selected the brain injury center at the University of Pennsylvania to treat and study the growing number of U.S. government workers who fell ill, a group that now includes at least one confirmed patient affected while serving in China.

Earlier this year, the Penn doctors published a study in the Journal of the American Medical Association that detailed vision, balance and hearing problems among the Cuba patients. They concluded that their symptoms are similar to mild traumatic brain injury, also known as concussion, but with no blow to the head.

Although the Miami doctors are no longer treating the patients, they emphasized that their study is critical to illustrating the symptoms and findings that patients demonstrated during the "acute" phase of their injury, soon after the suspicious sounds and sensations. Hoffer had previously sought to publish his study in the prestigious New England Journal of Medicine, U.S. officials said, before ultimately publishing it in the lower-profile otolaryngological journal on Wednesday.

Hoffer and his colleagues say they're not able to say for sure whether the patients have traumatic brain injury, which is notoriously difficult to diagnose. But they say they're definitive that the patients have injuries to the inner ear, which includes sensitive organs that control balance and interact heavily with the vision system.

"That problem alone can account for cognitive issues," Hoffer said. "There could easily be an injury in the brain. We just don't know that."

In his press conference in Havana, Cuba's Fernandez de Cossio emphasized a longstanding complaint that the U.S. has been unwilling to jointly investigate the incidents with Cuba's government or to let the Cubans have access to the medical records of the American patients.

"Until today there are no real facts, nor analyses based on science," he said. "And there is no evidence that can prove that something happened in Cuba that could harm the health of some American diplomats."