The U.S. State Department has brought a group of diplomats home from Guangzhou, China, over concern they were suffering from a mysterious malady that resembles a brain injury and has already affected U.S. personnel in Cuba, a spokeswoman said.
In China, one diplomat who experienced the symptoms left in April; this week, another American and his family left to return to the United States for treatment and testing. A spokesperson for the State Department confirmed to The Associated Press that "a number of individuals" had been brought to the USA for further testing.
According to experts who studied the previous cases in Cuba, those afflicted so far in Cuba and Guangzhou - suffered injuries consistent with a concussion without ever having received a blow to the head.
The Americans who were evacuated worked at the US Consulate in the southern city of Guangzhou, and their colleagues and family members are being tested by a State Department medical team, officials said. The U.S. also expelled 15 Cuban officials from its embassy in Washington.
Washington has said in the past that Cuban authorities must take responsibility for the safety of U.S. diplomats on their soil, but the Havana government denies any knowledge of an attack.
Reacting to the reports of the mysterious sound attacks on the U.S. diplomats, Foreign Ministry spokesperson Hua Chunying told a media briefing on Thursday that Beijing had investigated the May 23 allegation and found no clue.
Symptoms have included dizziness, headaches and an inability to concentrate.
Security guards outside the Guangzhou consulate checked reporter's IDs on Thursday and told them to leave the area and not attempt to talk to consulate staff.
Secretary of State Mike Pompeo released a statement on Tuesday saying the department established a task force last month "to direct a multi-agency response to the unexplained health incidents". "If there is really some problem, U.S. can directly connect and communicate with China and China will adopt a responsible attitude to investigate this", she said.
China earlier said it had looked into the case announced last month but came up with no clues about the cause of the symptoms.
People working in Canton Place, a few kilometers (miles) from the consulate said they were just hearing about the incidents, reflecting a lack of coverage in China's entirely state-controlled media.
The State Department has said it suspects the stricken diplomats in Cuba were purposely targeted for an attack.
Aled Williams, a British teacher at a kindergarten said Thursday that the reports sounded "sci-fi-ish".
"It's very odd. But I don't feel that there's something to be very afraid of because it's probably a very special case", Chen said.
"Relevant authorities of China have conducted investigations and given the feedback to the US. But I don't feel that there's something to be very afraid of because it's probably a very special case", Chen said.