The US embassy in China issued on Friday its second health alert to its citizens in two weeks after more US government employees were evacuated from the country over fears they may have been hit by a mysterious illness. American officials sent a medical team to the southern city of Guangzhou last month after an employee attached to the consulate there was diagnosed with brain trauma after experiencing strange sounds. The case revived fears that a US rival has developed some kind of acoustic or microwave device after similar symptoms were reported among American diplomats and their families in Cuba in 2016. The US embassys latest health alert said that following voluntary medical screenings, the State Department "has sent other individuals to the United States for further evaluation". There have been reports that the evacuated Americans are being taken for testing to the University of Pennsylvania. Thats where doctors have been treating and studying patients evacuated from the US Embassy in Havana.  The message of the embassy in China urges staff and family members to contact their health care provider if they experience "any unusual, unexplained physical symptoms or events, auditory or sensory phenomena, or other health concerns". "Symptoms to be attentive for include dizziness, headaches, tinnitus, fatigue, cognitive issues, visual problems, ear complaints and hearing loss, and difficulty sleeping," the alert says. The message urges people to "not attempt to locate the source of any unidentified auditory sensation" and instead move to a different location. The State Department, which reported the latest medical evacuations on Wednesday, has not accused any particular country or organization of being behind the latest incidents. The Chinese foreign ministry said Thursday that its investigation into the first case has not yielded any clues as to the cause of the incident. "As for the latest incident, my understanding is that the US side hasnt had any formal communication with the Chinese side about it," foreign ministry spokeswoman Hua Chunying said Thursday at a regular press briefing. The State Department has previously said brain injuries suffered by 24 US officials and family members posted in Havana could have been the result of a "health attack", perhaps from an unidentified secret weapon. In testimony before the Senate Foreign Relations Committee last month about the first case in China, US 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."