The State Department has said Americans who worked at the embassy in Cuba were targeted for attacks that began late last year and continued at least until late summer this year. (Yamil Lage/AFP/Getty Images)

Injuries have been confirmed to two more State Department personnel stationed in Havana, bringing to 24 the number of verified cases linked to mysterious and unexplained attacks on U.S. Embassy staff in Cuba.

State Department spokeswoman Heather Nauert said Friday that the new medical assessments involved incidents that happened earlier this year.

"They do not reflect new attacks," she said, noting that the most recent medically confirmed case happened in late August.

Nauert acknowledged also that the number of victims may grow.

"Our personnel are receiving comprehensive medical evaluations and care," Nauert said. "We can't rule out additional new cases as medical professionals continue to evaluate members of the embassy community."

The State Department has said Americans who worked at the embassy were targeted for attacks that began late last year and continued at least until late summer this year. The victims include diplomats, intelligence officers and their spouses.

Their symptoms, sometimes verified months after the attacks, include hearing loss, balance problems and traumatic brain injuries. In some cases, the embassy personnel fell ill after hearing unusual noises, either in their residences or in hotels. That has led to speculation they may have been the victims of some form of sonic attack, but investigators have not been able to replicate it or conclusively prove it.

The Cuban government, which has denied having anything to do with the injuries, has allowed FBI agents onto the island to investigate, in addition to conducting its own investigation. But neither has been able to pinpoint a cause, much less the source of it.

The maladies have led to the greatest crisis in U.S.-Cuban relations since the two countries normalized their relationship in 2015 and reestablished embassies. The United States has ordered all but essential personnel to leave Havana and prohibited almost all U.S. officials from traveling there unless they are investigating the cases or doing necessary work at the embassy.

Washington also has expelled more than half of the Cuban diplomats based in the United States and issued a travel warning advising Americans not to visit Cuba.

President Trump has suggested that he believes Cuba is responsible for what has happened to the embassy personnel. State Department officials have been more circumspect, saying Cuba has not met its requirement under the Vienna Convention to protect diplomats.