WASHINGTON (Reuters) - Two more people from the U.S. Embassy in Havana are undergoing medical evaluation, a State Department spokeswoman said on Friday, after a mysterious illness began to affect U.S. personnel and family members there since late 2016.

Further details were not available on the evaluations. “These are potentially new cases, but they are not yet medically confirmed,” the spokeswoman said.

U.S. experts have yet to determine who or what was behind the mysterious illnesses that affected 24 people. Cuban officials, who are conducting their own investigation, have denied any involvement or any knowledge of what was behind it.

The Associated Press first reported there were two possible additional cases in Cuba on Friday.

The administration of U.S. President Donald Trump, which has partly rolled back a detente with Cuba, responded last year by sharply drawing down U.S. Embassy staff in Havana and in October expelled 15 Cuban diplomats.

Symptoms suffered by the diplomats have included hearing loss, tinnitus, vertigo, headaches and fatigue, a pattern consistent with “mild traumatic brain injury,” State Department officials have said.

In April, Canada said it would remove families of diplomats posted at its embassy in Cuba as information from medical specialists has raised concerns of a new type of brain injury.

The U.S. State Department said on Wednesday it has brought a group of diplomats home from Guangzhou, China, over concern they were suffering from a mysterious malady that resembles a brain injury and has already affected U.S. personnel in Cuba.