Police in the city of Berlin announced that they are conducting investigations after employees of the US Embassy complained of symptoms of what is known as “Havana Syndrome”.
An investigation into the possibility of targeting embassy staff with special sound effects began in August, police said.
More than 200 US officials have complained of symptoms of the syndrome since 2016.
And US President Joe Biden pledged Friday to get to the truth of the syndrome and those behind it.
Those who have experienced the phenomenon say they feel a sudden pressure in their heads and hear a strange buzzing coming from a specific direction. Others complained of dizziness, nausea, fatigue and other symptoms.
According to a report by the German magazine Der Spiegel, many employees of the US Embassy in Berlin have reported that they suffer from symptoms of the syndrome.
An embassy spokesman declined to comment on the German police investigation, but told Reuters news agency that US authorities were investigating incidents in various parts of the world.
President Biden’s pledge came after signing a bill that would guarantee better health care and financial assistance to victims of the phenomenon, but he described it as a “health anomaly” rather than referring to an attack from a hostile party.
He said that American employees, intelligence officers, diplomats and military personnel in different parts of the world suffered from the phenomenon.
The mysterious disease was first noticed at the US and Canadian embassies in Havana in 2016, and since then there have been multiple reports of the phenomenon.
A CIA bureau chief in Vienna was dismissed last month after failing to properly deal with the mystery phenomenon at the embassy, where more cases have been observed than anywhere in the world, with the exception of Havana.
The flight of US Vice President Kamala Harris from Singapore to the Vietnamese capital, Hanoi, was delayed slightly after a US official reported the symptoms referred to.
The cause of the symptoms remains a mystery, and an American scientific committee concluded last year that the most likely guess is that it is caused by energy or directed vibrations.
A 2018 study of diplomats who experienced the phenomenon in Cuba found that they had suffered a brain injury, and it was not determined what caused it, but the researchers said it was most likely caused by directed microwaves.
And last July, William Burns, the director of the CIA, said that the symptoms were caused by deliberate targeting and that Russia may be behind it, but Moscow strongly denied responsibility for this.
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