Security workers guard at construction site of the U.S. Consulate compound in Guangzhou in southern China's Guangdong province in October 2009. The State Department said Wednesday, June 6, 2018, that it is evacuating several Americans amid health concerns about mysterious symptoms arising after unusual noises detected by U.S. diplomats and their families working in the consulate. (AP/AP file)

The State Department is evacuating several Americans from China amid health concerns about mysterious symptoms arising after unusual noises detected by U.S. diplomats and their families working in the consulate in Guangzhou.

After initial screenings by a medical team dispatched last month when the first incident was reported, the State Department has sent “a number” of ­affected people to the United States for further evaluation, State Department spokeswoman Heather Nauert said.

The evacuation was the first sign that the unexplained ailments previously known to have afflicted only one U.S. government employee in China have now broadened and threaten to become a full-blown health crisis like the one that affected at least 24 U.S. diplomats and their families in Cuba.

The latest round of evacuations began Wednesday in China, on what was still Tuesday in the United States. More diplomats and their dependents are expected to be sent home in coming days. U.S. officials declined to specify exactly how many people are likely to be returned for more testing after initial screenings were conducted on dozens of diplomats and family members.

“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.

On May 23, the State Department issued a health alert for China after revealing that one employee of the Guangzhou consulate had reported hearing strange noises and exhibiting symptoms of brain injury. The State Department described his experience as “subtle and vague, but abnormal, sensations of sound and pressure,” and ordered his evacuation. The State Department said at the time that it was unaware of any similar situation elsewhere in China, either among diplomats or outside the diplomatic community.

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 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.

Last month, Secretary of State Mike Pompeo noted the striking similarities between the one reported case in China and those experienced by at least 24 Americans connected to the U.S. Embassy in Havana. Many of them were diagnosed with signs of minor brain trauma, like concussions, after hearing eerily disturbing noises starting in late 2016 and continuing through most of last year.

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.

Now, the phenomenon appears to have spread halfway around the world.

The illnesses in China come amid increasingly strained relations between Washington and Beijing.

The U.S. military recently uninvited China from participation in a major international naval exercise, citing continued Chinese militarization of the South China Sea. Weeks earlier, the Pentagon accused the Chinese military of directing blinding lasers at American pilots in East Africa.

Meanwhile, a possible trade war between the United States and China is still looming, with the White House threatening to press ahead with tariffs on $50 billion in Chinese goods later this month.

President Trump is due to meet North Korean leader Kim Jong Un in Singapore on June 12 to hold talks on nuclear disarmament, the success of which will probably depend in part on cooperation from the Chinese. The Trump administration is also holding talks with the Chinese government on what steps Beijing could take to avoid the imposition of the tariffs the White House has been threatening.

The incidents in Guangzhou deepen a medical mystery that began affecting American government personnel in Havana in 2016. 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 they “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.