According to several senior State Department officials, the U.S. believes that last fall, several State Department employees at the U.S. embassy were attacked in Havana, Cuba. The assailants, who are still unknown, used sonic devices and at least two victims were injured enough to be brought back to the U.S. for treatment.
The Cuban government has been investigating the incident since it was made aware last February.
The U.S. kicked out two Cuban diplomats in May for safety reasons, because they were unsure if the Cuban government was involved. The Cuban government strongly denies their involvement.
To convince the U.S., they allowed the F.B.I. to come onto their land to help with the investigation.
There were several incidents where employees at different places were attacked, either inside or outside the residences of U.S. diplomats living in Havana. One official said the employees could have permanent hearing loss and will have to use a hearing aid from now on.
Since the incidents, they suffered a variety of symptoms which resembled concussions like nausea, headaches and dizziness.
The investigation is still ongoing.