WASHINGTON — American diplomats who served in Cuba have been diagnosed with mild traumatic brain injury following mysterious, unexplained attacks on their health, the union that represents U.S. diplomats said Friday, in the most detailed account to date of the growing list of symptoms.

In addition to mild TBI — commonly called a concussion— permanent hearing loss has been diagnosed among the 10 diplomats who have met with or spoken to the American Foreign Service Association. The union did not say how many of the 10 had been given either diagnosis, but said other symptoms had included brain swelling, severe headaches, loss of balance and “cognitive disruption.”

The union said in a statement that it “strongly encourages the Department of State and the U.S. Government to do everything possible to provide appropriate care for those affected, and to work to ensure that these incidents cease and are not repeated.”

What transpired in Havana in late 2016 and early 2017 has remained an elusive mystery as U.S. investigators continue looking for a device or other possible cause for what the State Department has described as attacks on diplomats’ health. Early indications from U.S. officials had pointed to a possible covert sonic device, although investigators have not said such a device has been found. The State Department has said it still can’t conclude who was responsible for the attacks.

The confirmation that diplomats suffered traumatic brain injury suggested the attacks caused more serious damage than the hearing-related complaints that were initially reported.

Traumatic brain injury, or TBI, typically results from a bump, jolt or other external force that disrupts normal brain functioning, according to the U.S. Centers for Disease Control and Prevention. Short- and long-term effects can include changes to memory and reasoning, sight and balance, language abilities and emotions.

Not all traumatic brain injuries are the same. Doctors evaluate patients using various clinical metrics such as the Glasgow Coma Scale, in which a numerical score is used to classify TBIs as mild, moderate or severe.

The State Department has said at least 16 Americans associated with the U.S. Embassy in Havana suffered symptoms from attacks. But the U.S. has declined to describe their symptoms or current conditions, other than to say the “incidents” that affected them are no longer occurring.

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AP Medical Writer Lauran Neergaard contributed to this report.