(WASHINGTON) — In his first message to all staff on the issue, Secretary of State Antony Blinken on Thursday acknowledged there is “growing concern” about the “unexplained health incidents” that have affected dozens of U.S. personnel around the globe.

Blinken committed to meeting “soon” with staff and families affected by what’s commonly called “Havana syndrome,” after the first cluster of cases were reported in Cuba’s capital in late 2016.

Amid some complaints that the department has not been proactive enough in addressing their health challenges or other issues, the note, obtained first by ABC News, acknowledged some shortcomings in sharing information with the department’s 70,000 employees and supporting those who have been impacted.

“Those of you who’ve been directly affected are urgently seeking clarity. Employees going abroad are anxious about whether they or their families are at risk. That’s completely understandable, and I wish we had more answers for you,” wrote Blinken.

“We can and will do a better job keeping you informed of our efforts to get answers, support those affected, and protect our people,” he added.

President Joe Biden’s National Security Council is leading a government-wide investigation into what is causing the incidents and who may be behind them. But so far, U.S. officials have few answers, nearly five years after State Department, CIA, and other personnel at the U.S. embassy in Havana reported strange experiences, like feelings of pressure or vibration and a screeching sound, and debilitating symptoms, including headaches, nausea, cognitive deficits, and trouble with seeing, hearing, or balancing. Several officials have been diagnosed with traumatic brain injuries.

Since then, cases have been reported in several other countries, including China, Uzbekistan, Russia, Austria, and the United States, although it’s unclear how many U.S. officials have confirmed medical symptoms.

“The investigation into what’s causing these incidents and how we can protect our people is ongoing,” Blinken wrote in his message.

Last December, the National Academies of Sciences, Engineering, and Medicine issued a report that concluded that “directed, pulsed radio frequency energy appears to be the most plausible mechanism in explaining these cases, especially in individuals with the distinct early symptoms.”

The CIA, State Department, and Pentagon all have their own internal task forces to address cases among their personnel and search for possible clues into the causes. The State Department’s is overseen by Pamela Spratlen, a two-time ambassador, while the CIA assigned a veteran officer critical to the agency’s efforts to find Osama bin Laden to now head its cell.

In addition, the State Department started a pilot program to begin recording baseline medical information of personnel and their adult family members before they move to U.S. diplomatic posts overseas.

Similarly, the CIA has tripled the number of full-time medical personnel focused on the issue, according to its director Bill Burns. He told NPR two weeks ago that while the symptoms are “real, and it’s serious,” the agency still has no definitive answers on the cause.

This is a developing story. Please check back in for updates.

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