A US Secret Service agent suffered a stroke while on duty during President Trump's visit to Scotland.
He was part of the presidential protection team during Mr Trump's stay at the Turnberry golf resort in Ayrshire.
In a statement, US officials said he was receiving "much needed critical care".
Police Scotland, the NHS, and the Scottish Ambulance Service said they were unable to provide any details.
'We are incredibly grateful'
The agent fell ill on Sunday, prompting the Secret Service to release a statement.
It said: "On 15 July a US Secret Service Special Agent suffered a cerebrovascular accident in Scotland, UK where he was travelling in support of Presidential Protection.
"The Secret Service asks for your prayers and continued respect for the agent and his family's privacy.
"We are incredibly grateful for the emergency medical service providers and physicians in Scotland who are providing much needed critical care."
The agency would not provide any further information on where the agent was being treated.
President Trump left Turnberry on Sunday, flying out of Prestwick Airport to Helsinki, Finland, ahead of talks with Russian president Vladimir Putin on Monday.