Updated

Two more Americans have been confirmed to be affected by unexplained health attacks against U.S. diplomats in Cuba, the United States said Tuesday, raising the total number of victims to 21.

The additional two individuals appear to be cases that were only recently reported but occurred in the past. The State Department said no new, medically confirmed "incidents" have taken place since the most recent one in late August. Earlier this month, the U.S. disclosed there had been another incident in August after previously saying the attacks had stopped.

It's possible the number could grow even higher as more cases are discovered. State Department spokeswoman Heather Nauert said the U.S. continues to assess American personnel.

The U.S. citizens were members of the American diplomatic community, the U.S. said. Officials have said previously that the incidents, deemed "health attacks" by Secretary of State Rex Tillerson, affected diplomats posted to the Embassy in Havana along with family members who live with them.

The U.S. didn't say how serious the newly disclosed incidents were. But the State Department said it was providing "the best possible medical evaluation and care" throughout the ordeal, including aid from a medical officer on staff at the embassy.

The union representing American diplomats has said mild traumatic brain injury is among the diagnoses given to some diplomats victimized in the attacks. The American Foreign Service Association has said permanent hearing loss was another diagnosis, and additional symptoms had included brain swelling, severe headaches, loss of balance and "cognitive disruption."

The evolving U.S. assessment indicated investigators were still far from any thorough understanding of what transpired in the attacks, which started in the fall of 2016. The U.S. has described them as unprecedented.

As the bizarre saga has unfolded, the U.S. has encouraged its diplomats to report any strange physical sensations. So it's unclear whether some symptoms being attributed to the attacks might actually turn out to be unrelated.

Notably, the U.S. has avoided accusing Cuba's government of being behind the attacks. The U.S. did expel two Cuban diplomats, but the State Department emphasized that was in protest of the Cubans' failure to protect the safety of American diplomats while on their soil, not an indication the U.S. felt that Havana masterminded it.

U.S. investigators have been searching to identify a device that could have harmed the health of the diplomats, believed to have been attacked in their homes in Havana, but officials have said no device had been found.