BEIJING — The State Department issued a health alert to U.S. citizens in China on Wednesday after an American government worker suffered a mild traumatic brain injury following mysterious “sensations of sound and pressure.”

The warning follows the U.S. urging Americans not to visit Cuba following sonic incidents there that sickened 21 embassy staffers and their families, and comes as Secretary of State Mike Pompeo prepares to meet Chinese Foreign Minister Wang Yi in Washington later Wednesday to discuss trade.

The employee in China, who was assigned to the southern port city of Guangzhou, “reported subtle and vague, but abnormal, sensations of sound and pressure,” according to the alert.

“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 continued.

“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. Instead, move to a location where the sounds are not present.”

Jinnie Lee, a spokeswoman for the U.S. Embassy in Beijing said the employee reported the symptoms from late 2017 through last month and was eventually taken to the U.S. for further evaluation.

“On May 18, the embassy learned that the clinical findings of this evaluation matched mild traumatic brain injury,” she said. “The department is taking this incident very seriously and is working to determine the cause.”

The Chinese government has promised to investigate, she added.

Cuba has repeatedly denied any involvement in the incidents reported in Havana, and in September invited the FBI to Cuban capital to investigate. But neither government has determined who is responsible. "Some very bad things happened in Cuba," President Donald Trump said at the time. "They did some bad things."

The tourism warning has prompted a drop in visitors to Cuba following a record year in 2017.

Guangzhou, which has a population of about 14.5 million, lies across the Pearl River from Hong Kong.

Mac William Bishop reported from Beijing, and Alastair Jamieson reported from London.