An American flag is flown next to the Chinese national emblem during a welcome ceremony for visiting U.S. President Donald Trump outside the Great Hall of the People in Beijing. Credit: Andy Wong | AP

The Chinese government still has no idea why a U.S. diplomat fell ill at the consulate in Guangzhou after hearing mysterious sounds, despite completing its investigation Thursday.

On Wednesday, the State Department said it was evacuating several more Americans from Guangzhou for further health screenings. That follows the initial evacuation of a government employee, who had reported hearing strange noises in his apartment and exhibiting symptoms of brain injury.

On Thursday, China’s Foreign Ministry said it had looked into the case after being told about the first incident.

“China and relevant authorities conducted an investigation and gave feedback to the United States,” spokeswoman Hua Chunying told a regular news conference. “We haven’t found the cause or clues that would lead to the situation mentioned by the United States.”

Hua said the Foreign Ministry had not yet been formally informed by the U.S. government about the new cases, having only heard about them through media reports.

“If the United States communicates with us, we will adopt a responsible attitude to investigate this,” she said. “We will maintain communication with the United States on this.”

Last month, Secretary of State Mike Pompeo told Congress the case in Guangzhou was medically very similar to the ones seen in Cuba last year, when a large part of the embassy staff was withdrawn after complaining of symptoms that included hearing loss, dizziness, tinnitus, visual difficulties, headaches and fatigue.

The American Foreign Service Association said then that government employees had been diagnosed with “mild traumatic brain injury and permanent hearing loss, with such additional symptoms as loss of balance, severe headaches, cognitive disruption, and brain swelling.”

In Guangzhou, the first employee to be evacuated complained of “subtle and vague, but abnormal, sensations of sound and pressure,” according to the State Department. Now more cases have come to light, with “a number” of affected people sent to the United States for further evaluation, according to State Department spokeswoman Heather Nauert.

A U.S. medical team in Guangzhou was also screening more Americans Thursday, the Associated Press reported.

The latest round of evacuations, which began Wednesday in China, was the first sign that the unexplained ailments have now broadened and threaten to become a full-blown health crisis like the one that affected at least 24 diplomats and their families in Cuba.

A U.S. official, who wasn’t authorized to discuss the situation publicly and requested anonymity, told the Associated Press, that the evacuated Americans are being brought for testing to the University of Pennsylvania, where doctors have been treating and studying patients evacuated from the embassy in Havana.

“U.S. medical professionals will continue to conduct full evaluations to determine the cause of the reported symptoms and whether the findings are consistent with those noted in previously affected government personnel or possibly completely unrelated,” Nauert said.

Though no names were released, a Foreign Service officer, Mark Lenzi, told The Washington Post he would be evacuated along with his wife and three-year-old son.

Lenzi said he began hearing unusual sounds in April 2017, comparing them to rolling marbles with static. He said he started experiencing excruciating, painful headaches a few months later, as did his wife and son.

Lenzi also said the employee evacuated last month was his next-door neighbor, a fellow Foreign Service officer who was diagnosed with mild traumatic brain injury.

The State Department has said it suspects the stricken diplomats in Cuba were purposely targeted for an attack. In response, it downsized the U.S. diplomatic staff in Havana and prohibited families from joining the diplomats who stayed. The United States also expelled 15 Cuban diplomats in retaliation, accusing Cuba of failing to protect American envoys.

But despite an investigation by the FBI that has gone on for more than a year, U.S. officials have been unable to determine the cause of the injuries, much less who the perpetrators might be.

An examination of more than 20 affected individuals, conducted by University of Pennsylvania researchers and later published in the Journal of the American Medical Association, concluded that the staff affected in Cuba “appeared to have sustained injury to widespread brain networks without an associated history of head trauma.”

The study identified a “constellation of acute and persistent signs and systems” — including cognitive dysfunction, headaches and sleep abnormalities — following exposure to “directional and audible sensory phenomena.”

Other researchers subsequently criticized the methods used in the study, saying that the neuropsychological evidence the article presented was flimsy.

Separately, a group of researchers at the University of Michigan suggested that a poorly engineered ultrasonic transmitter, designed to eavesdrop on conversations, could have caused the injuries in Cuba. They said their experiments managed to replicate the metallic chirping sounds U.S. diplomats heard in conjunction with the attacks in Cuba, raising the likelihood that the injuries were the result of ultrasonic signals.

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