The US State Department has confirmed it has evacuated government employees in Southern China, after unexplained health concerns were raised.
The health issues have been likened to another event in 2016, where US investigators suspected a sonic attack on employees.
Symptoms of the attack include dizziness, headaches and an inability to concentrate with unexplained sounds.
Chinese Foreign Ministry spokeswoman Hua Chunying said that the US has raised no formal complaints with Beijing.