One more U.S. Embassy employee in Havana, Cuba, has been affected by mysterious health incidents, the State Department said.

State Department spokeswoman Heather Nauert said one of two Americans recently evacuated from Cuba was "medically confirmed" to have been affected, while the other was "still being evaluated" by doctors.

25 Americans affected

In all, 25 Americans have been affected by the mystery ailment in Cuba.

"We still don't know, to this day, what is causing it and who is responsible," Nauert said, noting that investigations were underway in Havana as well as Guangzhou, China, where one employee experienced similar symptoms recently.

The United States has said that the Cuba incidents started in late 2016. The State Department calls them "specific attacks" but has not said what caused them or who was behind them. Cuba has adamantly denied involvement or knowledge.

Initial speculation centered on some type of sonic attack owing to strange sounds heard by those affected, but an interim FBI report in January found no evidence that sound waves could have caused the damage, The Associated Press has reported.

Warning issued in China

The State Department issued a health warning after the employee in China reported experiencing "subtle and vague, but abnormal, sensations of sound and pressure" and was diagnosed with a mild traumatic brain injury.

Secretary of State Mike Pompeo described it as a "serious medical incident."

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The new confirmation came less than a week after the U.S. renewed demands on Cuba to determine the source of the "attacks" on U.S. diplomats. Cuba responded by again denying any involvement in or knowledge of any such attacks. (VOA)