GUANGZHOU, China (AP) — The U.S. Embassy in China sent its second alert in two weeks Friday to its citizens over unexplained health issues that have prompted the evacuation of a number of U.S. government employees working at a consulate in a southern city.

The alert urged Americans to seek medical help in the event they suffered any "unusual, unexplained physical symptoms or events, auditory or sensory phenomena, or other health concerns."

The alert comes as a U.S. medical team is screening more Americans who work at the Guangzhou consulate. A previous case in Guangzhou, disclosed last month, prompted the tests.

The incidents have raised fears the unexplained issues that started in Cuba in 2016 have expanded to other countries. China says it has uncovered no information that could point to a cause.

The most recent evacuations followed medical testing that revealed they might have been affected. State Department spokeswoman Heather Nauert said "a number of individuals" had been brought to the U.S. but didn't say how many were affected or evacuated.

Friday's alert called for people to be attentive of symptoms including "dizziness, headaches, tinnitus, fatigue, cognitive issues, visual problems, ear complaints and hearing loss, and difficulty sleeping." It urged them "not to attempt to locate the source of any unidentified auditory sensation. Instead, move to a different location."

The U.S. government has deemed the Cuba incidents "specific attacks" on American workers but hasn't publicly identified a cause or culprit. Most of the incidents were accompanied by bizarre, unexplained sounds that initially led U.S. investigators to suspect a sonic attack.

Asked about the latest incidents, Chinese Foreign Ministry spokeswoman Hua Chunying said Thursday that the U.S. had not formally raised the matter with Beijing.

"If the U.S. makes formal contact with us, China will continue necessary investigations in an earnest and responsible manner and maintain close communication and cooperation with the U.S.," Hua said at a regularly scheduled news conference.

China earlier said it had looked into the case announced last month but came up with no clues about the cause of the symptoms.

A U.S. official, who wasn't authorized to discuss the situation publicly and requested anonymity, said the evacuated American government workers were being brought from China for testing to the University of Pennsylvania. That's where doctors have been treating and studying patients previously evacuated from the U.S. Embassy in Havana.

The preliminary findings of the medical reports on the 24 personnel affected in Cuba showed they had sensory and memory problems similar to the brain dysfunction seen with concussions.

The Penn team said the patients from Cuba experienced persistent disability though rehabilitation therapy customized for them seemed to help.

Canada in April also ordered families of diplomatic staff in Cuba to return home after mysterious health symptoms were detected in 10 Canadians stationed on the island. Canada said the 10 continued to show unexplained brain symptoms and that "medical information raised concerns for a new type of a possible acquired brain injury."

In testimony before the Senate Foreign Relations Committee last month about the first case in China, U.S. Secretary of State Mike Pompeo said China had "said all the right things and have demonstrated their willingness to help us identify the vector which led to this medical incident."

The China incidents affect one of the most important of the seven U.S. diplomatic outposts in the country. The Guangzhou consulate opened months after the establishment of diplomatic relations between Beijing and Washington in 1979 and moved to its new purpose-built facility in 2013.

It serves four southern provinces with a combined population of more than 204 million and processes more than 1 million visa applications of all types annually. It is also the only U.S. diplomatic installation in China authorized to process immigrant visas and handle adoptions.

People working in The Canton Place complex, a few kilometers (miles) from the consulate, said Thursday they were just hearing about the incidents, reflecting a lack of coverage in China's entirely state-controlled media.

Aled Williams, a British teacher at a kindergarten said Thursday that the reports sounded "sci-fi-ish."

"Hard to get my head around how it works," he said. "Better watch myself."

Linda Chen, who runs a coffee shop in the area, said she was mystified as to why only certain people seemed to have been affected in an area known for its comfort and safety.

"For me I feel it's very strange. But I don't feel that there's something to be very afraid of because it's probably a very special case," Chen said.

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Associated Press writer Josh Lederman in Washington, D.C. contributed to this report.