Transcript for New details on illnesses of US diplomats in Cuba

New developments into the investigation into what caused U.S. Officials to fall ill in Cuba. We are now learning more about what may have led to hearing and memory loss and whether it involved a sonic attack. ABC's Victor Oquendo is in Miami with all of those details. Good morning. Reporter: Good morning, Amy. Some of those officials were medically evacuated right here to Miami for immediate treatment. This happened months ago but the investigation is still very much ongoing. This morning, troubling new information about those American officials working in Havana, Cuba, who suddenly fell ill. Yes, there is a pattern taking place here. Yes, there is something -- there is something going on. Reporter: But the U.S. Government doesn't know exactly what happened or who was behind it and now several government agencies including the FBI are on the ground in Havana to find out what why at least ten American staff members and their families started experiences strange and severe physical symptoms in late 2016 including hearing loss and according to our Miami station WPLG memory loss, loss of balance and vision issues. Sources telling ABC they appeared to have been targeted by a sonic device that produced inaudible and audible booms, impossible to hear with the human ear much like a dog whistle. Tony, are you there? Reporter: It sounds like something out of a Hollywood movie, not even iron man was a match for this sonic device but in real life they can cause permanent damage. If this is a type of weapon, the type of device that could be used in other places, I think there's real reason for the state department to be concerned about our diplomats in other countries where we have tense relations. Reporter: While the investigation deepens those officials that returned home are being treated and closely monitored by doctors. Those incidents have caused a variety of physical symptoms. Not everyone has experienced the same type of symptoms. Reporter: Cuba denying any involvement but in response the U.S. Expelled two Cuban diplomats from Washington, D.C. According to the state department, there are American staff mes who chose to stay and continue working in Havana and for them medical professionals were brought in for an evaluation. Amy. All right, Victor, thank,you. We appreciate it.

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