The United States is investigating potential cases of Havana syndrome in the South American nation of Colombia, US media reported.
The investigation comes a week ahead of US Secretary of State Antony Blinken’s scheduled travel to Bogota next week.
US embassy staff in Bogota may have been injured by the mysterious illness, which causes a painful sound in the ears, fatigue and dizziness.
The Wall Street Journal first reported the illness quoting an email received by US Ambassador to Colombia Philip Goldberg, of a number of “unexplained health incidents” since mid-September.
Colombian President Iván Duque said the country is investigating the reports. He added that the US is leading the inquiry.
Americans who have been hit by Havana syndrome have described an intense and painful sound in their ears. Some of the estimated 200 affected have been left with dizziness and fatigue for months.
The mysterious illness first emerged at the US and Canadian embassies in Havana in 2016. Since then there have been a number of similar reports.
Last month the CIA’s station chief in Vienna was removed for failing to respond appropriately to an outbreak of the mysterious syndrome at the embassy, where there have been more recorded cases than any other city apart from Havana.
Days earlier a CIA officer who was travelling to India with the agency’s director reported symptoms consistent with Havana syndrome.
And in August, Vice President Kamala Harris’ flight from Singapore to the Vietnamese capital Hanoi was briefly delayed after an American official reported symptoms.
However, the cause of the illness remains unclear. Last year, a US National Academy of Sciences panel found that the most plausible explanation was “directed, pulsed radio frequency energy”.
And in 2018 a scientific study of diplomats affected in Cuba found that they had experienced a form of brain injury. The cause was not conclusively determined, but researchers said it was most likely the result of directed microwave radiation.
In July, CIA director William Burns said there was “a very strong possibility” that the symptoms were being caused deliberately and that Russia could be responsible. However, Moscow has strongly denied responsibility.