The State Department has urged U.S. citizens in China to report any "symptoms or medical problems" they notice while in the country to a medical professional after a government employee experienced "subtle and vague, but abnormal, sensations of sound and pressure." The report comes after multiple U.S. and Canadian nationals suffered from what the U.S. government called "health attacks" in Cuba.

The employee at the U.S. Consulate in the southeastern Chinese city of Guangzhou has been left with mild traumatic brain injury, and was sent home in April, U.S. officials tell CBS News. The U.S. embassy and consulates in China have held town hall meetings to give employees a chance to ask questions, CBS News correspondent David Martin reports.

"A U.S. government employee in China recently reported subtle and vague, but abnormal, sensations of sound and pressure," the U.S. State Department said in its health advisory posted online Wednesday. "The U.S. government is taking these reports seriously and has informed its official staff in China of this event. We do not currently know what caused the reported symptoms and we are not aware of any similar situations in China, either inside or outside of the diplomatic community."

Get Breaking News Delivered to Your Inbox

A spokesperson at the U.S. Embassy in Beijing confirmed to CBS News that from late 2017 through April 2018, a U.S. government employee assigned to the Guangzhou Consulate reported "a variety of physical symptoms." The employee was brought to the United States for medical evaluation and on May 18 the Embassy learned that the clinical findings of the evaluation showed mild traumatic brain injury (MTBI).

The embassy spokesperson told CBS News that the Chinese government had "assured us they are also investigating and taking appropriate measures."

Wednesday morning, Secretary of State Mike Pompeo spoke on the Guangzhou health alert to the House Foreign Affairs Committee, calling it a serious incident.

"The medical indications are very similar -- and entirely consistent with -- the medical indications that have taken place to Americans working in Cuba," Pompeo said.

Pompeo met with China's foreign minister, who said it is investigating and hasn't found anyone who could be responsible for the possible sonic attacks, Martin reports.

Pompeo told the House committee that medical teams are being moved to address the issue.

More than 20 Americans who had worked or travelled in Cuba reported a range of medical symptoms beginning in November 2016, U.S. officials told CBS News last year. According to medical records first obtained by CBS News, a U.S. doctor diagnosed the American diplomats as suffering from mild traumatic brain injury. Symptoms included headaches and hearing loss. Former U.S. Secretary of State Rex Tillerson said in Sept. 2017 the American diplomats were victims of "health attacks."

In October, a State Department official said the U.S. had "received a handful of reports from U.S. citizens who report they experienced similar symptoms following stays in Cuba."

However, U.S. investigators haven't determined who or what was behind the alleged attacks.

"Twenty-four people have had symptoms and findings consistent with what looks like a mild traumatic brain injury," State Department medical director Dr. Charles Rosenfarb told a Senate Foreign Relations subcommittee Jan. 9. "The findings suggest that this is not an episode of mass hysteria."

In response, the State Department reduced its Havana embassy to a skeleton staff, and ordered 15 Cuban embassy officials in the U.S. to leave the country.