A security officer stands next to the U.S. Embassy in Havana, Cuba, June 8, 2018. REUTERS/Alexandre Meneghini/File Photo

WASHINGTON (Reuters) - The U.S. State Department said another person had been affected by health problems at the U.S. Embassy in Cuba, bringing to 26 the number of Americans who have suffered mysterious maladies in that country.

The latest case and another confirmed on June 21 were found to involve health effects similar to those reported by other members of the U.S. Havana diplomatic community and were the first since August 2017, the department said in a statement.

U.S. experts have yet to determine who or what was behind the mysterious illnesses, which began in late 2016. Cuban officials, who are conducting their own investigation, have denied any involvement or any knowledge of what was behind it.

The State Department statement said the two cases confirmed this month “result from a single occurrence in late May in a diplomatic residence in which both officers were present.” They raised the number of Americans affected to 26, it said.

The administration of U.S. President Donald Trump, which has partly rolled back a detente with Cuba, first charged diplomats were the victims of “sonic attacks” and Cuba as the host country was at a minimum responsible for their safety.

Washington last year sharply reduced U.S. Embassy staff in Havana and in October expelled 15 Cuban diplomats.

Symptoms suffered by those affected 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 had raised concerns of a new type of brain injury.

The U.S. State Department said this month it had brought a group of diplomats home from Guangzhou, China, over concerns they were suffering from a malady that resembles a brain injury.