In an alert emailed to U.S. citizens in China, the Embassy said it does not know what caused the symptoms.
The Trump administration is taking these reports seriously and have taken up the matter with Chinese officials.
“A US State Department government employee in China recently reported subtle and vague, but abnormal sensations of sound and pressure,” the U.S. Embassy in China said.
“We do not currently know what caused the reported symptoms and we are not aware of any similar situations in China, either inside or outside of the diplomatic community,” it said.
According to the reports, the U.S. and Chinese authorities are investigating the matter.
The employee, who was assigned to the southern city of Guangzhou, was diagnosed with mild traumatic brain injury (MTBI), said Embassy spokeswoman Jinnie Lee.
“It’s a serious medical incident. We want to make sure and take care of every one of our officers serving overseas. We’ve learnt about it only recently. We are still trying to identify all the circumstances surrounding it,” said U.S. Secretary of State Mike Pompeo.