Former Olympic Council of Ireland (OCI) president Pat Hickey has been released from Bangu Prison in Rio.
Mr Hickey was being held in relation to alleged mis-selling of tickets for the Olympic Games.
A judge in Rio recommended on Monday that Mr Hickey be released from prison and placed under house arrest.
The OCI said in a statement on Tuesday that it "welcomes the release of Mr Pat Hickey".
In his own statement Mr Hickey confirmed he had been released from prison but would stay in Rio.
He said: "My lawyers will proceed to have the charges laid against me set aside as there is no substantive proof of any wrong doing on my part."
'Kindness'
"I would like to thank the prison authorities for their kindness they have shown to me," he added.
"Due to my medical condition, I will be making no further statements."
The judge said his release would not "put at risk the public order, or the application of penal law".
Precautionary imprisonment
Timeline: Olympic ticket-sale scandal
He added that precautionary imprisonment can only be used when the maximum time servable for an offence exceeds four years, which is not the case here.
Earlier this month, Mr Hickey temporarily stood down from his roles as Olympic Council of Ireland president and European Olympic Committees' president. Mr Hickey, 71, was detained by Brazilian police on Wednesday 17 August but was then taken to hospital for tests after he complained of health problems.
He was later transferred to the high-security prison.
Irish Sports Minister Shane Ross has ordered an inquiry into the ticketing claims.
Other OCI officials
Three other OCI officials are still in Rio after they had their passports seized by Brazilian police investigating the ticketing scandal.
In a statement from the OCI it said that the "three OCI officials are due to have their passports returned over the coming days and we look forward to welcoming Kevin Kilty, Stephen Martin and Dermot Henihan home shortly."
The executive committee of the European Olympic Committees has also welcomed the news of Mr Hickey's move to house arrest.