A U.S. government employee in southern China reported abnormal sensations of sound and pressure, the State Department said Wednesday, recalling similar experiences among American diplomats in Cuba who later fell ill.

In an emailed notice to American citizens in China, the department said it wasn’t currently known what caused the symptoms in the city of Guangzhou, where an American consulate is located.

“A U.S. government employee in China recently reported subtle and vague, but abnormal, sensations of sound and pressure,” the notice said. “The U.S. government is taking these reports seriously and has informed its official staff in China of this event.”

The department said it wasn’t aware of any similar situations in China, either within the diplomatic community or among others. It didn’t further identify the person with the symptoms or say when they had been detected.

China’s foreign ministry and National Health Commission did not immediately respond to faxed questions about the report.

U.S. Secretary of State Mike Pompeo is to meet in Washington on Wednesday with Chinese Foreign Minister Wang Yi. They are expected to focus on the planned U.S.-North Korea summit, but U.S. concerns about the incident in Guangzhou are likely to be raised.

Despite hundreds of billions of dollars in annual trade between them, China and the U.S. are considered strategic rivals for influence in Asia. Tensions in the relationship frequently flare over accusations of cheating at trade, stealing of secrets, human rights and arms sales to Taiwan, a U.S. partner that China claims as its own territory.

In Cuba, the U.S. reported that some of its personnel and family members experienced a range of ailments, often after hearing an unusual sound. For most, the symptoms occurred around May 2017.

The still-unexplained incidents sparked a rift in U.S.-Cuban relations, while investigators have chased theories including a sonic attack, electromagnetic weapon or a flawed spying device.

Last October, the State Department ordered non-essential embassy personnel and the families of all staff to leave Havana, arguing the U.S. could not protect them from unexplained illnesses that have harmed at least 24 Americans.

Symptoms, sounds and sensations reportedly varied dramatically from person to person. Some have permanent hearing loss or concussions, while others suffered nausea, headaches and ear-ringing. Some are struggling with concentration or common word recall, The Associated Press has reported.

Some felt vibrations or heard loud sounds mysteriously audible in only parts of rooms, and others heard nothing.

(AP)