The Olympic Council of Ireland is investigating an allegation that an Irish competitor at the London Games previously bet on an opponent to win an event in which they were both competing.
A spokesman said the council has informed the athlete, whom it will not name, about an anonymous allegation that two bets were made in favour of an opponent in an unspecified sport prior to the Olympics.
The spokesman said it was now a legal issue and that the council would not make any further comment at this time.
Ireland has over 60 athletes taking part in 14 sports at the Games, which officially opened last night.
Athletes are banned from betting during the Games.
The International Olympic Committee has pledged to crack down on illegal gambling and has set up a monitoring unit to track betting patterns.
Sanctions are severe and athletes could face exclusion from the games.