The entrance of the U.S. Consulate in Guangzhou, China. (Sue-Lin Wong/Reuters)

A Chinese government investigation has shed no light on why a U.S. diplomat fell ill at the consulate in Guangzhou after hearing mysterious sounds, an official said Thursday.

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

On Thursday, the Chinese Foreign Ministry said investigators 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 said at 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 that the case in Guangzhou was medically similar to the ones seen in Cuba last year, when a large part of the American Embassy staff was withdrawn after many complained of symptoms that included hearing loss, dizziness, tinnitus, visual difficulties, headaches and fatigue.

The American Foreign Service Association said then that the 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,” the State Department said. Now more cases have come to light, with “a number” of affected people sent to the United States for further evaluation, said State Department spokeswoman Heather Nauert.

A U.S. medical team in Guangzhou was also screening more Americans on 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 was not authorized to discuss the situation publicly and spoke on the condition of anonymity, told the Associated Press that the evacuated Americans were being brought for testing to the University of Pennsylvania, where doctors have been treating 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 3-year-old son. Lenzi said he began hearing unusual sounds in April 2017, comparing them to rolling marbles with static. He said he started suffering excruciating headaches a few months later, as did his wife and son.

Lenzi also said the employee evacuated last month was his 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 lasted more than a year, U.S. officials have been unable to determine the cause of the injuries, much less identify the perpetrators.

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 presented in the article was flimsy.

Separately, a group of researchers at the University of Michigan suggested that ultrasound signals from two or more transmitters could have accidentally interfered with each other to produce an audible signal.

The ultrasound signals could have come from eavesdropping devices, from jammers meant to block eavesdropping, or even from ultrasound pest repellents, the researchers said, raising the possibility that whatever or whoever caused the noise may have had no intent to harm. 

Morello reported from Washington.