Police in Brazil have arrested the head of the European Olympic Committees, Irishman Patrick Hickey, in Rio over illegal Olympic ticket sales.
Mr Hickey, 71, is suspected of being involved in a scheme to sell tickets for higher than their face value.
He was taken to hospital after his arrest as a precaution, where he will probably spend the night, police said.
When officers went to his hotel room on Wednesday morning they found his wife there with his Olympic credentials.
Mrs Hickey said her husband had left for Ireland at the weekend, police told a news conference.
With the help of the hotel they began a search and found Mr Hickey in the room next door, they said.
While police said they had reason to believe he was trying to escape, a video apparently of the arrest on the ESPN Brazil sports news website shows Mr Hickey answering the door naked to officers.
Police said the arrest was related to that of fellow Irishman Kevin James Mallon on the day of the Olympic opening ceremony.
They estimate the potential profits of the alleged scheme at 10m reals (£2.4m; $3.1m).
The International Olympic Committee (IOC) said it would co-operate with any police investigation.
Irish broadcaster RTE reports that Mr Hickey faces three potential charges: facilitating ticket touting, forming a cartel, and “ambush” marketing.
A spokesman for Ireland’s Department of Foreign Affairs and Trade told the BBC: “We are aware of an Irish citizen having been arrested in Rio. The department, through its consulate in Rio, is following up and stands ready to provide all appropriate consular assistance.”
Sports minister Shane Ross, who is in Rio and who met Mr Hickey at the weekend to discuss the ticket sales allegations, tweeted simply: “Shell shock here in Rio.”
The OCI said in a statement it was “aware of the media stories regarding Pat Hickey and we are seeking total clarity on the situation before we comment further”.
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Mr Hickey is president of the European Olympic Committees, the body which gathers the continent’s 50 national Olympic committees together.
His passport and Olympic ID were seized and were later displayed to photographers at the press conference.