May 23 (UPI) -- The U.S. Embassy in China issued a health alert Wednesday to all government workers after an employee showed signs of a brain injury after hearing "abnormal" sounds and feeling unusual physical pressure.
"The U.S. government is taking these reports seriously and has informed its official staff in China of this event," the embassy said in a statement.
The State Department said the employee, stationed in Guangzhou, shows symptoms of a mild traumatic brain injury.
The embassy warned workers in China to move away from the source of the noise if they experience "any unusual acute auditory or sensory phenomenon" with "unusual sounds of piercing noises."
Embassy spokeswoman Jinnie Lee said the employee reported the symptoms beginning late last year and they lasted through April. The worker was sent back to the United States for medical evaluation.
"The embassy learned that the clinical findings of this evaluation matched mild traumatic brain injury," Lee said. "The department is taking this incident very seriously and is working to determine the cause."
The incident appears similar to unexplained "sonic attacks" on diplomats at the U.S. Embassy in Cuba last year.
Multiple workers in Havana complained of an incapacitating "high pitch beam of sound." The State Department ultimately confirmed 21 cases in Cuba.
The diplomats said when they left rooms in the embassy, the symptoms and sounds immediately stopped. Officials believe some type of sonic weapon may have been used.
The diplomats described concussion-like symptoms like hearing loss, dizziness, balance problems, visual complaints, headaches, fatigue, cognitive issues and difficulty sleeping.