London (CNN) -- An $11.7 million win at a London casino by top American poker player Phil Ivey has been referred to the British Gambling Commission, a source familiar with the casino confirmed Monday after media reports surfaced that the payout was being withheld.
Ivey hit a winning streak over two nights in August playing punto banco at Crockfords, Britain's oldest private gaming club, according to The Daily Mail newspaper. The source, who declined to be identified because he has been asked by Crockfords not to speak about the case, confirmed the accuracy of the Daily Mail report.
The source did not provide details of why the win was referred to the commission, which regulates commercial gambling, and said the casino has not had contact with legal representatives for Ivey.
Both the gambling commission and Crockfords declined to comment.
Ivey could not be reached Monday for a response to the reports.
Punto banco is a form of the baccarat card game favored among high-rollers.
Ivey, 35, has won eight World Series of Poker bracelets and more than $6.2 million during his career. With his sixth-place ranking in the WSOP and his penchant for playing high-stakes, the organization calls him "arguably the best poker player in the world."