– A crisis over a mysterious ailment sickening U.S. diplomats and their families — which began in Cuba and recently appeared in China — widened on Wednesday. The State Department evacuated at least two more Americans who fell ill in China after hearing strange noises, officials said.

Many other employees at the U.S. Consulate in the southern Chinese city of Guangzhou and their family members are also being tested by a State Department medical team that has been flown in, officials said. It is unclear how many of them are exhibiting symptoms, but officials expect more U.S. personnel to be evacuated.

For months, U.S. officials have been worried that their diplomats have been subjected to targeted attacks involving odd sounds, leading to symptoms similar to those “following concussion or minor traumatic brain injury,” the State Department says.

The new illnesses come just weeks after U.S. officials reported finding their first case in Guangzhou, where a consulate employee got sick after reporting disturbing noises.

The illnesses have broadened a medical mystery that started in 2016, when U.S. Embassy employees and their family members began falling ill in Havana. In all, 24 of them were stricken with headaches, nausea, hearing loss, cognitive issues and other symptoms after saying they heard odd sounds. The issue has roiled relations with Cuba, which immediately fell under suspicion, and led the United States to expel Cuban diplomats.

But it remains unclear whether the illnesses are the result of attacks at all. Other theories have included toxins, listening devices that accidentally emitted harmful sounds or even mass hysteria.

The mystery spread to China this spring, when the first employee fell ill, and fears escalated last month when the government warned other employees to seek medical attention if they experienced unusual ailments. So far this week, Mark A. Lenzi, a security engineering officer at the consulate, his wife and their two children were evacuated after the parents exhibited neurological symptoms in recent months. The illnesses appear more widespread than the State Department reported last month, when it said that one person had “reported subtle and vague, but abnormal, sensations of sound and pressure.”

Secretary of State Mike Pompeo said last month at a hearing of the House Foreign Affairs Committee that the symptoms of the first U.S. employee in Guangzhou to report being ill “are very similar and entirely consistent with the medical indications that have taken place to Americans working in Cuba.”

There are roughly 170 American diplomats or employees in Guangzhou, as well as their family members, and a senior U.S. official said a sizable number had undergone or would soon undergo testing by the State Department doctors who arrived on May 31. Officials cautioned that no determination had been made about what caused the illnesses.

The sounds and vibrations have been described variously as the sounds made by cicadas, static, metal sheets waving or marbles rolling around a metal funnel.

They did not occur at the consulate itself, which opened in 2013 and is a state-of-the-art building designed to withstand electronic eavesdropping and other security and intelligence threats. Instead, the ailing employees said they experienced the strange sounds and sensations in at least two apartment complexes where American government workers live, along with other foreigners and wealthy Chinese.