About 100 CIA officers and family members are among about 200 US officials and kin sickened by “Havana syndrome”, the CIA director, William Burns, said on Thursday, referring to the mysterious set of ailments that include migraines and dizziness.

Burns, tapped by Joe Biden as the first career diplomat to serve as CIA chief, said in a National Public Radio interview that he had bolstered his agency’s efforts to determine the cause of the syndrome and what is responsible.

He confirmed that among other steps, he had tapped a senior officer who once led the hunt for Osama bin Laden to head a taskforce investigating the syndrome, and said he had tripled the size of the medical team involved in the investigation.

The agency also had shortened from eight weeks to two weeks the time that CIA-affiliated people must wait for admission to Walter Reed national military medical center, he said.

“It’s a profound obligation, I think, of any leader to take care of your people and that is what I am determined to do,” Burns told NPR in his first interview since becoming CIA director in March.

Havana syndrome, with symptoms such as dizziness, nausea, migraines and memory lapses, is so named because it first was reported by US officials based in the US embassy in Cuba in 2016.

Burns noted that a US National Academy of Sciences panel in December found that a plausible theory was that “directed energy” beams caused the syndrome.

There was a “very strong possibility” that the syndrome was intentionally caused, and that Russia could be responsible, he said, adding that he was withholding definitive conclusions pending further investigation.

Moscow denies involvement.