Story highlights "We can confirm another incident which occurred last month and is now part of the investigation" the State Department said

Two US diplomats suffered long-term injuries including hearing loss as a result of the attacks

(CNN) The State Department announced Friday that incidents of acoustic attacks on US diplomats in Havana, Cuba, which have led to a variety of serious medical symptoms, continued until as recently as last month.

"As we've said previously, an investigation into the incidents is ongoing, and we revise our assessments as we receive new information," State Department Spokeswoman Heather Nauert said in a statement. "We can confirm another incident which occurred last month and is now part of the investigation."

"Based on continued assessments of personnel, there are now 19 confirmed U.S. government personnel who have been affected," she added, updating her previous count of "at least 16 US government employees."

Last week, Nauert said the incidents, which began in late 2016, appeared to have ceased.

Earlier on Friday, a labor union representing US diplomats expressed concern Friday over the severity of symptoms resulting from the recent suspected "sonic harassment."

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