The Defense Department has spent more than a year testing a device purchased in an undercover operation that some investigators think could be the cause of a series of mysterious ailments impacting spies, diplomats and troops that are colloquially known as Havana Syndrome, according to four sources briefed on the matter.

US diplomats may have been targeted by Russian sonic weaponry, say the Insider, Der Spiegel and CBS’s 60 Minutes

After long denying the possibility, some intelligence agencies are no longer willing to rule out a mystery weapon.