Key figures in the OCI investigation
The key figures in the probe
A native of Bangor in County Down, Stephen Martin is the chief executive of the Olympic Council of Ireland and is based in its headquarters in Howth.
A talented sportsman, he won an Olympic gold medal with the Great Britain hockey team at the Seoul Olympics in 1988 having picked up a bronze medal with the team four years earlier in Los Angeles.
He has more than 100 caps for Ireland in the sport and is a former captain of the team. He is a close friend of former Ryder Cup golfer David Feherty - they went to school together in Bangor Grammar School. Martin himself is also a talented golfer and once won the Irish schoolboy golf championship. Even though he is the top paid official within the OCI, he has always maintained a low-key public profile.
Thrust into the limelight this week in Rio after Pat Hickey was arrested, Mr O'Brien faced media questions when he visited him in hospital before the latter's transfer to prison.
Prior to this controversy erupting, Hickey had indicated that he was stepping down as president of the OCI after the Rio Olympics and Mr O'Brien - the 'first' vice-president - would be taking over.
Mr O'Brien has a long association with the sport of archery, serving as general and international secretary as well as president of the organisation. He was the sport's delegate to the OCI for 12 years before being appointed Deputy Chef de Mission of the Irish team for the Sydney Olympics. Four years later in Athens, he served as Chef de Mission.
This ought to have been the best week in the sporting life of Dermot Henihan, with an Irish rowing squad finally winning an Olympic medal. A native of Limerick, Mr Henihan has had a lifelong association with the sport.
He served in various executive positions with the Irish Rowing Union and was manager of seven Irish Olympic rowing and world championship squads. He was deputy Chef de Mission of the Irish Olympic team in Athens and Chef de Mission of the team four years later in Beijing in 2008. He is the current honorary general secretary of the Olympic Council of Ireland.
Mr Kilty is the Chef de Mission of the Irish team in Rio. From the sport of clay pigeon shooting, he became the performance director of the organisation in 2006 after retiring as an international shooter. He was the shooting team leader and coach for the Beijing and London Olympics.
He is an executive board member of the International Shooting Sports Federation and various other international shooting organisations. But he has no public profile in Ireland.
Ms O'Reilly is Pat Hickey's personal assistant and has been involved in the OCI since 1992.