There are far more cases of a mysterious illness suffered by overseas US personnel dubbed 'Havana syndrome' than previously known, according to a new report.
In 2016 US officials in Havana, Cuba started reporting nausea, headaches and dizziness, often accompanied by a metallic buzzing sound. Since then more cases have been reported in China and now - revealed for the first time this week by the New York Times - there have been cases reported in Europe.
More than 130 people have been affected by the condition, more than twice as many as previously reported.
The cause remains unknown, but there have been suggestions it could be some kind of sonic or microwave-powered weapon.
"As of now, we have no definitive information about the cause of these incidents, and it is premature and irresponsible to speculate," Amanda J Schoch, spokeswoman for the Office of the Director of National Intelligence, told the Times.
Russia has denied being behind the alleged attacks, which seem to target diplomats, CIA employees and soldiers.
Some experts have suggested it could be psychological. Alan Carson, a neuropsychiatrist at The University of Edinburgh, told podcast Science Vs in April that was the likely scenario, unless a "brand new weapon" no one's ever seen before had been deployed.
But a new case suggests the syndrome is very real - in 2019 a military officer was "overcome by nausea and headaches" while driving into an intersection, the Times reported, and his two-year-old son in the back seat started crying. After they drove away from the intersection, he started to feel better - and his son also stopped crying.
Some have had ongoing headaches as a result of whatever has happened to them.
The CIA has set up a dedicated unit to get to the bottom of the mystery.
"We are bringing the US government's resources to bear to get to the bottom of this," said Emily J Horne, a spokeswoman for the US National Security Council.