NBC News first reported the bureau’s recognition of potential agent cases after the outlet received internal emails that showed an agent had reported possible brain injury symptoms after working in a country near Russia a decade ago.

About 200 American diplomats, officials, and their family members are believed to have been hit by the mysterious illness — described by the US government as “anomalous health incidents” – while overseas.

November 22, 2021

“This issue of anomalous health incidents is a top priority for the FBI, as the protection, health and well-being of our employees and colleagues across the federal government is paramount,” the bureau said in a statement, adding it would continue working with the intelligence community to “identify the causes of these incidents and determine how we can best protect our personnel.”

 WATCH: WHY WAS SEAN PENN SITTING FRONT & CENTER DURING JANUARY 6 'WITCH HUNT' SHOW TRIAL

Havana Syndrome is so-called because the first incidents of it were reported by US officials serving in Cuba in 2016. Symptoms include migraines, nausea, memory lapses, and dizziness.

November 22, 2021

The exact origin of Havana Syndrome is hidden, but many officials think it is rooted in radiation attacks carried out by Russia. The US government has never openly held any nation responsible for the incidents. A number of alternative solutions have been put forward — including that crickets are to blame for the disease.

 UP TO $6 BILLION NOW: BIDEN SENDING EVEN MORE CASH TO UKRAINE, CALLS IT RIDICULOUS NAME

Victims and lawmakers have lashed at federal agencies for not taking the illness seriously, and current and former officials told Reuters the FBI had previously been skeptical of agents’ reports of experiencing Havana Syndrome symptoms.

“The FBI takes all US government personnel who report symptoms seriously,” the bureau said in its statement.

 REPUBLICANS FIGHT OFF WOKE POLICIES IN NEW DEFENSE BUDGET

November 22, 2021

CIA Director William Burns recently put a career spy, who was involved in the search for Osama bin Laden, in charge of leading an investigation into the mysterious ailments. The agency also recalled its Vienna chief of station in September due, in part, to his claimed mishandling of reported Havana Syndrome cases.

The station chief, whose identity is highly classified, expressed doubt that the reports of illness were genuine, the Washington Post reported at the time.