Almost two dozen Americans who traveled to Cuba have reported experiencing similar symptoms to those suffered by U.S. diplomats serving at the American Embassy.

“Since September 29, the Department of State has been contacted by 19 U.S. citizens who reported experiencing symptoms similar to those listed in the Travel Warning after visiting Cuba,” a spokesperson for the State Department’s Bureau of Western Hemisphere Affairs told the Miami Herald via email.

At least 24 U.S. Embassy officials in Cuba had reported hearing loud, grating noises before experiencing ear issues, hearing loss, dizziness, headache, fatigue, cognitive issues and difficulty sleeping.

Doctors reportedly discovered the diplomats suffered from brain abnormalities, as the white matter in their brains had “developed changes.”

The U.S. has stood by their allegations that Cuba in some way deliberately attacked the American officials — which Cuba has adamantly denied — and earlier this month raised the possibility that a virus was deployed intentionally to infect workers.

Cuba’s defenders have argued the U.S. can’t be certain anyone was harmed intentionally, because no proof has been publicly presented.

It was earlier reported that officials believed the Americans were the victims of “sonic attacks,” but an FBI report, revealed by The Associated Press, said the U.S. has found no evidence that sonic waves were used to harm Americans in Havana.

The State Department’s latest Cuba travel advisory is at a “level 3,” which advises U.S. citizens to avoid traveling to the Caribbean nation “due to serious risks to safety and security.”

The Associated Press contributed to this report.