Fallon, who won the Irish Derby Sunday, made a brief appearance at a London police station Monday, The Independent reported.
Police charged Fallon and the others allegedly conspired to fix races between 2002 and 2004 and defrauded bettors using the online gambling service, Betfair. The two-year investigation was nicknamed Operation Crypton.
Two Yorkshire jockeys and former syndicate director Miles Rodgers were also caught in the sting.
The investigation began when Betfair turned over betting records to the Jockey Club, which regulates British racing, the newspaper said. The Jockey Club, in turn, gave the records to the police.