There have been several reports of possible sonic attacks at the US consulate in Guangzhou, China.
Cuba has denied targeting embassy staff, and the U.S. has not blamed the country's government for the suspected attacks.
US experts have yet to determine who or what was behind the mysterious illnesses that affected 24 people.
The State Department has sent a medical team to China to offer medical screenings to all American government workers and family members who want them.
Global Affairs Canada is working to determine if any Canadian diplomats in southern China have been affected by a mysterious ailment that has already sickened a number of American diplomats and bears similarities to the unexplained illness suffered by Canadian and US government workers in Cuba.
It warned of "unexplained physical symptoms or events, auditory or sensory phenomena", and said symptoms of the ailment included dizziness, headaches, tinnitus, fatigue, cognitive issues, visual problems, ear complaints, and hearing loss, as well as difficulty sleeping.
That's where doctors have been treating and studying patients previously evacuated from the U.S. Embassy in Havana.More news: Russian Federation defender plans Ramos treatment for Salah
The New York Times said that an employee evacuated from Guangzhou on June 6 likened the sounds he experienced to "marbles rolling around a metal funnel".
Security guards outside the Guangzhou consulate on Thursday told reporters to leave the area and not attempt to talk to consulate staff.
In 2017 in Cuba at least 22 American diplomat and their family members have suffered as a result of the mysterious "acoustic attack". 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".
Guangzhou is one of the most important of the USA diplomatic outposts in the country.
Two other officials said the individuals have been brought for testing to the University of Pennsylvania, where doctors have been evaluating, treating and studying Americans affected in Cuba previous year as well as nearly 10 new possible cases from a US consulate in China. 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.
"We did not find any cause or clue that leads to the mentioned situation by the United States", she asserted.