THE CIA has concluded that it is unlikely Russia or another foreign adversary is using microwaves or other forms of directed energy to attack hundreds of US officials who attribute symptoms associated with brain injuries to the so-called Havana syndrome.

Investigators have studied hundreds of cases reported globally by US intelligence officers, diplomats and military personnel, who have spoken of headaches, dizziness, nausea and other symptoms consistent with traumatic brain injuries.

Most cases under review by intelligence officers have been linked to other known medical conditions or to environmental factors, an official said on condition of anonymity, adding that in some cases, medical check-ups have revealed undiagnosed brain tumours or bacterial infections.

In a statement, CIA director William Burns said: “While we have reached some significant interim findings, we are not done.”

The first report of Havana syndrome date to a series of reported brain injuries in 2016 at the US embassy in Cuba.

At a news conference in Berlin today, Secretary of State Antony Blinken said that, after meeting with people who had reported cases, “there is no doubt in my mind that they have had real experiences, real symptoms and real suffering.”