A U.S. government employee in China suffered a mild brain injury after hearing “abnormal” sounds in an incident reminiscent of others in Cuba that prompted the State Department to withdraw most of its personnel.

The unidentified employee, who had been assigned to the southern city of Guangzhou, has returned to the U.S. for treatment, according to embassy spokeswoman Jinnie Lee. She said the department is taking the incident “very seriously.”

“The Chinese government has assured us they are also investigating and taking appropriate measures,” she said, according to the AFP news agency.

The U.S. Embassy in Beijing also issued an statement saying the employee recently reported “subtle and vague, but abnormal, sensations of sound and pressure.” The statement said anyone concerned about any symptoms should consult a medical professional.

“While in China, if you experience any unusual acute auditory or sensory phenomena accompanied by unusual sounds or piercing noises, do not attempt to locate their source,” the embassy said on its website. “Instead, move to a location where the sounds are not present.”

In 2016, U.S. government personnel in Cuba reported hearing weird, loud sounds along with feelings of changes in air pressure in their homes owned and maintained by the Cuban government as well as hotel rooms. Although there had been no history of head trauma, the symptoms reported were consistent with brain injury.

The diplomats described the sounds as “buzzing, grinding metal, piercing squeals and humming.”

An expert panel set up by the State Department last year said the initial findings were most likely related to “neurotrauma from a non-natural source” and recommended further investigation.

In March, the State Department made permanent its earlier decision to withdraw 60% of its diplomats from the island nation because of the health concerns.

Earlier, 15 Cuban embassy employees were ordered to leave the United States, although Washington has not formally charged Cuba with any deliberate attacks over the health issues.

Then-Secretary of State Rex Tillerson said in October that the U.S. was expelling the diplomats because of Cuba’s “failure to take appropriate steps to protect our diplomats” in Havana.

The move also was in line with increasingly strained relations between Cuba and the U.S. under the Trump administration.

In April, Canada also downgraded its presence in Cuba after several Canadian diplomats stationed in Havana complained of symptoms similar to those experienced by American diplomats.

Canada’s Ministry of Global Affairs said ongoing medical testing has raised the possibility of a “new type” of “brain injury” that doctors still can’t define.