Pat Hickey remains in hospital this morning and is unlikely to be moved to a police detention centre until this evening at the earliest.
The former head of the Olympic Council of Ireland (OCI), who was arrested yesterday morning at his hotel in Rio, was continuing to receive treatment at the Hospital Samaritano today.
A number of officials visited the health care centre last night and this morning.
Members of the Brazilian military police were also spotted outside the newly built hospital.
Shortly before 8am (local time) Dermot Heneghan, Secretary General of the OCI, arrived in an official car. He declined to speak to a small group of press that had gathered from early morning.
Last night William O'Brien, first vice president of the OCI, spoke briefly before entering the facility.
He told reporters, after visiting at around 7pm (local time): "We will defend ourselves to the hilt."
Mr O'Brien added: "Pat [Hickey] has been admitted to hopsital, his medical condition has been checked, he is stable at the moment, and it will be... in the next 24 hours. "So there is be nothing happening here over the next 24 hours."
Mr Hickey is facing three charges of facilitating ticket touting, formation of a cartel and ambush or illicit marketing.
Brazilian detectives say the offences carry a sentence of up to seven years in prison.
When asked about the three charges at the hospital last night Mr O'Brien said: "No comment because as you can understand he is having all sorts of tests inside, so he has made no comment about the allegations. We have really restricted access, that’s all I can tell you."
He added: "We will defend ourselves to the hilt, that's all I can tell you."
Mr Hickey was arrested in a dawn raid on his hotel room at 6am yesterday.
Police arrived at the Windsor Marapendi hotel in Rio de Janeiro to find his wife Sylviane alone in the bedroom, but her husband's possessions still in the room.
The Rio police said Mr Hickey's wife claimed that her husband had returned to Ireland.
Officers then began a search of the hotel and found Mr Hickey in his son's room.
He was then arrested by police on suspicion of the formation of a criminal association/cartel, ticket-touting and illicit marketing. The charges, if proven, carry a prison sentence of up to seven years.
Mr Hickey was accused of plotting with others to sell tickets above face value in a scheme that authorities say netted about €2.5m in profits
Police executed a warrant to detain him on suspicion that he was aware that tickets from the OCI had ended up with THG Sports, a company which is not accredited to sell Olympic tickets.
"This morning, we arrested the president of the Olympic Council of Ireland at a hotel in Barra da Tijuca (near the Olympic Park)," said Ronaldo Oliveira, the head of specialist operations at the Civil Police.
Shortly after his arrest Hickey was brought to the Samaritano Hospital near the Olympic Park after informing police he suffers from a heart condition.
Last night the OCI released a statement saying Mr Hickey would remain in the hospital for a period of 24 hours.
"Mr Patrick Hickey has been admitted for investigation of chest pain. His condition is stable. In view of his previous cardiac history he will remain in hospital for a further 24 hours
Brazilian police have also obtained court orders for the preventative detention of three suspects, all directors of Pro 10 Sports Management, the Irish-accredited seller of Olympic tickets which police believe diverted the tickets to THG. They are Michael Glynn, Ken Murray and the former footballer Eamonn Collins.
They add to the existing orders against Marcus Evans, the British owner of THG, and four other directors of that company, including Irishman Kevin James Mallon, who was arrested in Rio de Janeiro on August 5.
All face the same charges relating to an alleged €2.8m scam to sell prized tickets to Rio 2016 at up to 18 times face value. Police seized 823 high-end tickets from a THG executive arrested in Rio on August 5.
"Our detectives arrived at the hotel early," Mr Oliveira said. "When we arrived at the room registered to him, we found only his wife, who was sleeping.
"She lied, saying that he had already gone home to Ireland.
"But we saw that his shoes, socks and open suitcase in the room. We found him in another room registered to his son. There were hardly any personal possessions in that room. He is 71 and the doctor in the hotel said he was shaken. He was taken to hospital for tests before he will be released to police."
"Hickey has been involved in the Olympics for more than 20 years and we believe he knew everything that went on," detective Aloysio Falcão added.
Images by ESPN Brazil show Mr Hickey answering the door to police and then stepping into the bathroom naked.
Moments later, he walks out in a white bathrobe.
Police took his passport, Olympic credentials, Olympic tickets, three laptops, two mobile phones and a return air ticket for August 22. Last night Mr Hickey was being guarded at the Hospital Samaritano Barra.
Police said they believed that Pro 10 Sports Management, the current accredited reseller of Olympic tickets in Ireland, was created to allow the diversion of Irish Olympic tickets to THG, which sold them in Brazil for up to 18 times face value.
They also found some tickets in the possession of THG that were intended purely for the 'Olympic family' and could not be resold at all.
"The OCI had the right to sell the tickets directly, or through a reseller," the detective leading the probe for the Civil Police, Ricardo Barboza de Souza, said.
"But we have verified that these tickets were diverted to this other company, THG, who sought to tout them under the cover of a hospitality scheme.
"That is the dynamic of this conspiracy. It was done in this way to achieve a very high profit margin and to try and avoid a police investigation."
Tickets with a face value of €390 were being sold for up to €7,090, 18 times face value, said Mr Barboza de Souza.
Asked what proof police had against Mr Hickey, he said: "The OCI had an important commercial relationship with THG dating back to the Olympics in 2012 and 2014. We are continuing to investigate."
Detectives say they found emails on Mr Hickey's phone to and from Marcus Evans, the British owner of THG, who police are also seeking to arrest, dating back to 2010, as well as James Sinton, its then CEO, who was arrested for touting in Brazil in 2014.
In a series of emails in the past week, Mr Evans forwarded links to news articles and a statement by the company Pro 10 Sports Management, which is also ensnared in the scandal, to Mr Hickey, police said.
"We believe Evans was indirectly warning Hickey to watch out," Mr Falcão said.
Another email, from a law firm, urged Mr Hickey to put Sports Minister Shane Ross "back in his box" ahead of a meeting between the two.
The email, from Barry MacCarthy of law firm MacCarthy Johnston, Dublin, passes on the advice of Siobhán Phelan, who he said was a "senior counsel."
The email said: "In general, Shane Ross needs to be "put back in his box." You should say that at the moment an Irishman has been charged by the Brazilian authorities and is fundamentally entitled to due process and the presumption of innocence."
Last night Judge Mariana Tavares Shu, from a special Olympic court, confirmed the detention orders for Mr Hickey and his co-accused.
The order is to prevent any of those in Brazil from leaving, as happened with other individuals during a touting investigation during the 2014 World Cup.
This means that Mr Hickey will be detained in Rio when he is released from hospital.
The judge said: "All involved are foreigners and do not have permanent residence in this country, so it seems likely that, if they remained at liberty, they might avoid justice. I cite the example of James Sinton… of the Marcus Evans Group at the time of the World Cup 2014, who, once set free, escaped to his country of origin."
A spokesperson for the OCI said Mr Hickey complied fully with the terms of the warrant for arrest by the Brazilian authorities but that in light of his ill health, he would step aside. "Mr Hickey taken to hospital as a precautionary measure," they said.
"In light of the developments and his ill health, Mr Hickey has taken the decision to step aside temporarily as president of the OCI and all other Olympic functions until this matter is fully resolved. He will of course continue to co-operate and assist with all ongoing enquiries."
The other accused in the case are the owner of Ipswich Town Marcus Evans (52); David Patrick Gilmour (35); Kevin James Mallon (36); Martin Studd (49); and Martin van Os (45). Police say they have statements from seven Brazilians who bought hospitality packages, including Olympic tickets, from THG Sports for up to €7,000.
THG does not have permission to sell Rio 2016 tickets and police were called.
Mallon remains in custody.
Police said the tickets included for the opening and closing ceremonies and top athletics events, including the men's' 100-metre final. One family bought €69,000 worth, all of which were voided after the arrests, police said.
'Pat is probably the top-ranked Irish administrator in the world of international sport and, as well as being a prime mover in the IOC, he is president of the powerful European Olympic Committees organisation."