The “Havana Syndrome” remains a mystery: US intelligence services do not assume that a “foreign adversary” is responsible for the mysterious illnesses of US embassy employees. It’s about hundreds of cases of brain injury and other symptoms reported by American foreign officials in several countries.

A report released on Wednesday questioned long-held suspicions by those affected that they may have been the target of a global campaign by Russia or another country to attack Americans with some sort of directed energy. But there is still no alternative plausible explanation for the cases.

It’s a frustrating “puzzle,” the Washington Post quoted an intelligence official as saying on Wednesday. The secret services are open to new ideas and evidence.

According to the Washington Post, seven US secret services have reviewed well over a thousand cases in almost a hundred countries. Five of those authorities concluded that it was “very unlikely” that a foreign adversary using an energy source was responsible for the symptoms. One of the authorities committed to the rating “unlikely”, another abstained.

Last year, an independent panel of experts came to the conclusion that some cases of Havana syndrome could have been triggered by some kind of targeted use of electromagnetic radiation.

Since 2016, numerous US diplomats living in Havana, Cuba, and their families have complained of mysterious headaches, hearing loss, dizziness and nausea. The embassy staff was then reduced to a minimum.

Similar complaints were later reported in other parts of the world – including in Berlin. The US government did not rule out that this could be some kind of attack – but it has always emphasized that it does not know what is behind it.