The two largest operators in the emerging US daily fantasy sports (DFS) market, FanDuel and DraftKings, have defended the integrity of their games after a DraftKing employee was discovered to have used insider information to win cash tournaments on FanDuel.

Concerns were raised in the US media after line-up information for a DraftKings tournament, including data on how many entrants had selected certain players, was leaked by one of the company's employees last week.

The employee, a manager at DraftKings, later won $350,000 in a rival contest run by FanDuel, prompting claims that the individual secured the prize by accessing and using information which was not widely available to the public.

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