Fenerbahce have confirmed club president Aziz Yildirim was among a group of people arrested in Turkey on Sunday to face questioning over allegations of match-fixing.
Turkish media report that around 40 people, including officials and players from a number of clubs, have been detained following police raids across 15 cities.
The raids were part of an investigation into allegations of match-fixing in Turkish football last season.
In a message on their official website, Fenerbahce confirmed Yildirim was among those arrested.
The Turkish Football Federation also released a statement confirming the investigation and saying they were "closely monitoring the details".
Fenerbahce were crowned league champions last term, pipping Trabzonspor to the Super Lig title with a dramatic 4-3 win at Sivasspor on the final day.