Pat Hickey has been released on bail from the high-security Bangu Prison in Rio.
He has been placed under house arrest while the Brazilian courts process allegations of ticket touting against him.
Mr Hickey has released the following statement:
"I have been released from the police detention system. I will now stay in Rio and 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.
I would like to thank the prison authorities for their kindness they have shown to me. Due to my medical condition, I will be making no further statements."
The release comes after his lawyers successfully applied for the 71-year-old's release on health grounds.
Mr Hickey, who has stepped aside as President of the OCI, denies the allegations against him.
Journalist with Independent.ie Cathal McMahon says Mr Hickey didn't talk to the waiting media as he left the prison:
The Executive Committee of the European Olympic Committee has issued a statement welcoming his release.
“The EOC welcomes the news that Patrick Hickey has been released from preventative custody in Bangu maximum-security prison. We believe this was the correct decision as it respects the dignity and fundamental human rights of Mr. Hickey. The EOC respectfully requests that these rights continue to be respected, including the principle of proportionality when under criminal investigation and Mr Hickey’s presumption of innocence.
“The EOC Executive Committee fully respects the Brazilian judicial procedures and it is not our intention to comment on, nor question, any matter relating to a specific legal case in Brazil.”
This was echoed by the Olympic Council of Ireland, who also welcomed the news that three Irish OCI officials are to have their passports returned to them:
"The OCI welcomes the release on bail of Mr Pat Hickey from Bangu Prison earlier today.
"The OCI also welcomes the news that 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."